Revert "[V0 deprecation] Remove V0 CPU/XPU/TPU backends (#20412)"

This reverts commit e202dd2736.

.buildkite/scripts/hardware_ci/run-cpu-test.sh

@@ -66,10 +66,10 @@ function cpu_tests() {
     tests/quantization/test_compressed_tensors.py::test_compressed_tensors_w8a8_dynamic_per_token"
 
   # Run AWQ test
-  # docker exec cpu-test-"$NUMA_NODE" bash -c "
+  docker exec cpu-test-"$NUMA_NODE" bash -c "
-  #   set -e
+    set -e
-  #   VLLM_USE_V1=0 pytest -s -v \
+    VLLM_USE_V1=0 pytest -s -v \
-  #   tests/quantization/test_ipex_quant.py"
+    tests/quantization/test_ipex_quant.py"
 
   # Run chunked-prefill and prefix-cache test
   docker exec cpu-test-"$NUMA_NODE" bash -c "

.buildkite/scripts/hardware_ci/run-xpu-test.sh

@@ -26,5 +26,7 @@ docker run \
     --name "${container_name}" \
     "${image_name}" \
     sh -c '
+    VLLM_USE_V1=0 python3 examples/offline_inference/basic/generate.py --model facebook/opt-125m
+    VLLM_USE_V1=0 python3 examples/offline_inference/basic/generate.py --model facebook/opt-125m -tp 2
     VLLM_USE_V1=1 python3 examples/offline_inference/basic/generate.py --model facebook/opt-125m --block-size 64 --enforce-eager
 '

examples/online_serving/chart-helm/values.yaml

@@ -8,7 +8,7 @@ image:
   # -- Image tag
   tag: "latest"
   # -- Container launch command
-  command: ["vllm", "serve", "/data/", "--served-model-name", "opt-125m", "--enforce-eager", "--dtype", "bfloat16", "--block-size", "16", "--host", "0.0.0.0", "--port", "8000"]
+  command: ["vllm", "serve", "/data/", "--served-model-name", "opt-125m", "--dtype", "float32", "--block-size", "16", "--host", "0.0.0.0", "--port", "8000"]
 
 # -- Container port
 containerPort: 8000

tests/kernels/attention/test_attention_selector.py

@@ -36,8 +36,7 @@ DEVICE_REGULAR_ATTN_BACKENDS = {
 DEVICE_MLA_BLOCK_SIZES = {
     "cuda": [16, 64],  # CUDA supports both standard and extended block sizes
     "hip": [16, 1],  # HIP requires special handling for block_size=1
-    # "cpu": [16]  # CPU uses fixed block size from test cases
+    "cpu": [16]  # CPU uses fixed block size from test cases
-    "cpu": []  # FIXME(woosuk): Temporarily disable CPU tests
 }
 
 
@@ -82,14 +81,14 @@ def test_env(
         m.setenv("VLLM_MLA_DISABLE", "1" if use_mla else "0")
 
         if device == "cpu":
-            if not use_v1:
-                pytest.skip("CPU backend only supports V1")
-
             with patch("vllm.attention.selector.current_platform",
                        CpuPlatform()):
                 backend = get_attn_backend(16, torch.float16, torch.float16,
                                            block_size, False)
-            assert backend.get_name() == "TORCH_SDPA_VLLM_V1"
+            if use_v1:
+                assert backend.get_name() == "TORCH_SDPA_VLLM_V1"
+            else:
+                assert backend.get_name() == "TORCH_SDPA"
 
         elif device == "hip":
             with patch("vllm.attention.selector.current_platform",
@@ -205,14 +204,12 @@ def test_fp32_fallback(
         m.setenv("VLLM_USE_V1", "1" if use_v1 else "0")
 
         if device == "cpu":
-            if not use_v1:
-                pytest.skip("CPU backend only supports V1")
-
             with patch("vllm.attention.selector.current_platform",
                        CpuPlatform()):
                 backend = get_attn_backend(16, torch.float32, torch.float32,
                                            16, False)
-            assert backend.get_name() == "TORCH_SDPA_VLLM_V1"
+            assert (backend.get_name() == "TORCH_SDPA_VLLM_V1"
+                    if use_v1 else "TORCH_SDPA")
 
         elif device == "cuda":
             with patch("vllm.attention.selector.current_platform",

vllm/attention/backends/cpu_mla.py

@@ -0,0 +1,307 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+from dataclasses import dataclass
+from typing import Any, Dict, List, Optional, Tuple, Type
+
+import torch
+
+import vllm._custom_ops as ops
+from vllm._ipex_ops import ipex_ops
+from vllm.attention.backends.abstract import (AttentionBackend,
+                                              AttentionMetadataBuilder,
+                                              AttentionType,
+                                              is_quantized_kv_cache)
+from vllm.attention.backends.mla.common import MLACommonImpl, MLACommonState
+from vllm.attention.backends.torch_sdpa import TorchSDPAMetadata
+from vllm.utils import make_tensor_with_pad
+from vllm.worker.cpu_model_runner import ModelInputForCPUBuilder
+
+
+class CPUMLABackend(AttentionBackend):
+
+    @staticmethod
+    def get_name() -> str:
+        return "CPU_MLA"
+
+    @staticmethod
+    def get_metadata_cls() -> Type["CPUMLAMetadata"]:
+        return CPUMLAMetadata
+
+    @staticmethod
+    def get_builder_cls() -> Type["CPUMLAMetadataBuilder"]:
+        return CPUMLAMetadataBuilder
+
+    @staticmethod
+    def get_state_cls() -> Type["MLACommonState"]:
+        return MLACommonState
+
+    @staticmethod
+    def get_impl_cls() -> Type["CPUMLAImpl"]:
+        return CPUMLAImpl
+
+    @staticmethod
+    def get_kv_cache_shape(
+        num_blocks: int,
+        block_size: int,
+        num_kv_heads: int,  # assumed to be 1 for MLA
+        head_size: int,
+    ) -> Tuple[int, ...]:
+        return (num_blocks, block_size, head_size)
+
+    @staticmethod
+    def swap_blocks(
+        src_kv_cache: torch.Tensor,
+        dst_kv_cache: torch.Tensor,
+        src_to_dst: torch.Tensor,
+    ) -> None:
+        ops.swap_blocks(src_kv_cache, dst_kv_cache, src_to_dst)
+
+    @staticmethod
+    def copy_blocks(
+        kv_caches: List[torch.Tensor],
+        src_to_dists: torch.Tensor,
+    ) -> None:
+        ops.copy_blocks_mla(kv_caches, src_to_dists)
+
+    @staticmethod
+    def get_supported_head_sizes() -> List[int]:
+        return [576]
+
+
+@dataclass
+class CPUMLAMetadata(TorchSDPAMetadata):
+    # New for MLA
+    # Input positions for rotrary embeddings since for MLA the rotary
+    # position embeddings are applied inside the attention backend
+    input_positions: torch.Tensor = None
+
+    # required by MLACommonImpl
+    is_profile_run: bool = False
+
+
+class CPUMLAMetadataBuilder(AttentionMetadataBuilder[CPUMLAMetadata]):
+
+    def __init__(self, input_builder: ModelInputForCPUBuilder) -> None:
+        self.chunked_prefill = input_builder.chunked_prefill
+        self.input_builder = input_builder
+        assert not self.chunked_prefill, \
+            "chunked prefill is currently not supported"
+
+    def prepare(self):
+        self.input_data = self.input_builder.input_data
+
+    def build(self, seq_lens, query_lens, cuda_graph_pad_size, batch_size):
+        input_data = self.input_data
+        prefill_seq_lens = seq_lens[0:input_data.num_prefills]
+        prefill_query_lens = query_lens[0:input_data.num_prefills]
+        slot_mapping = torch.tensor(input_data.slot_mapping,
+                                    dtype=torch.long,
+                                    device="cpu")
+
+        # metadata for prefill
+        if input_data.num_prefills > 0:
+            query_lens_tensor = torch.tensor(prefill_query_lens,
+                                             dtype=torch.int32,
+                                             device="cpu")
+            kv_lens_tensor = torch.tensor(prefill_seq_lens,
+                                          dtype=torch.int32,
+                                          device="cpu")
+            query_start_loc = torch.zeros(input_data.num_prefills + 1,
+                                          dtype=torch.int32,
+                                          device="cpu")
+            kv_start_loc = torch.zeros(input_data.num_prefills + 1,
+                                       dtype=torch.int32,
+                                       device="cpu")
+            torch.cumsum(query_lens_tensor,
+                         dim=0,
+                         dtype=torch.int32,
+                         out=query_start_loc[1:])
+            torch.cumsum(kv_lens_tensor,
+                         dim=0,
+                         dtype=torch.int32,
+                         out=kv_start_loc[1:])
+            max_query_len = max(prefill_query_lens)
+            max_kv_len = max(prefill_seq_lens)
+
+            # for chunked-prefill
+            if self.chunked_prefill:
+                prefill_block_tables = make_tensor_with_pad(
+                    self.input_data.prefill_block_tables,
+                    pad=0,
+                    dtype=torch.int32,
+                    device="cpu",
+                )
+            else:
+                prefill_block_tables = None
+
+        else:
+            query_start_loc = None
+            kv_start_loc = None
+            max_query_len = None
+            max_kv_len = None
+            prefill_block_tables = None
+
+        # metadata for decode
+        if input_data.num_decode_tokens != 0:
+            seq_lens_tensor = torch.tensor(
+                input_data.seq_lens[input_data.num_prefills:],
+                dtype=torch.int32,
+                device="cpu",
+            )
+            block_tables = make_tensor_with_pad(
+                self.input_data.decode_block_tables,
+                pad=0,
+                dtype=torch.int32,
+                device="cpu",
+            )
+        else:
+            block_tables = torch.tensor([])
+            seq_lens_tensor = torch.tensor(
+                input_data.seq_lens[:input_data.num_prefills],
+                dtype=torch.int32,
+                device="cpu",
+            )
+
+        # For multi-modal models
+        placeholder_index_maps = None
+        if len(input_data.multi_modal_inputs_list) != 0:
+            placeholder_index_maps = {
+                modality: placeholder_map.index_map()
+                for modality, placeholder_map in
+                input_data.multi_modal_placeholder_maps.items()
+            }
+
+        return CPUMLAMetadata(
+            chunked_prefill=self.chunked_prefill,
+            seq_lens=prefill_seq_lens,
+            seq_lens_tensor=seq_lens_tensor,
+            max_query_len=max_query_len,
+            max_kv_len=max_kv_len,
+            prefill_query_start_loc=query_start_loc,
+            kv_start_loc=kv_start_loc,
+            max_decode_seq_len=input_data.max_decode_seq_len,
+            num_prefills=input_data.num_prefills,
+            num_prefill_tokens=input_data.num_prefill_tokens,
+            num_decode_tokens=input_data.num_decode_tokens,
+            block_tables=block_tables,
+            prefill_block_tables=prefill_block_tables,
+            slot_mapping=slot_mapping,
+            multi_modal_placeholder_index_maps=placeholder_index_maps,
+            enable_kv_scales_calculation=False,
+            input_positions=torch.tensor([self.input_data.input_positions]))
+
+
+class CPUMLAImpl(MLACommonImpl[CPUMLAMetadata]):
+
+    def __init__(
+            self,
+            num_heads: int,
+            head_size: int,
+            scale: float,
+            num_kv_heads: int,
+            alibi_slopes: Optional[List[float]],
+            sliding_window: Optional[int],
+            kv_cache_dtype: str,
+            blocksparse_params: Optional[Dict[str, Any]],
+            logits_soft_cap: Optional[float],
+            attn_type: str,
+            kv_sharing_target_layer_name: Optional[str],
+            # MLA Specific Arguments
+            **mla_args) -> None:
+        super().__init__(num_heads, head_size, scale, num_kv_heads,
+                         alibi_slopes, sliding_window, kv_cache_dtype,
+                         blocksparse_params, logits_soft_cap, attn_type,
+                         kv_sharing_target_layer_name, **mla_args)
+
+        unsupported_features = [
+            alibi_slopes, sliding_window, blocksparse_params, logits_soft_cap
+        ]
+        if any(unsupported_features):
+            raise NotImplementedError(
+                "CPUMLAImpl does not support one of the following: "
+                "alibi_slopes, sliding_window, blocksparse_params, "
+                "logits_soft_cap")
+
+        if attn_type != AttentionType.DECODER:
+            raise NotImplementedError("Encoder self-attention and "
+                                      "encoder/decoder cross-attention "
+                                      "are not implemented for "
+                                      "CPUMLAImpl")
+
+        # states is implemented.
+        if is_quantized_kv_cache(self.kv_cache_dtype):
+            raise NotImplementedError(
+                "CPUMLAImpl with FP8 KV cache not yet supported")
+
+    def _forward_prefill(
+            self,
+            q: torch.Tensor,
+            kv_c_normed: torch.Tensor,
+            k_pe: torch.Tensor,
+            kv_c_and_k_pe_cache: torch.Tensor,
+            attn_metadata: CPUMLAMetadata,  # type: ignore[override]
+    ) -> torch.Tensor:
+
+        prefill_metadata = attn_metadata.prefill_metadata
+        assert prefill_metadata is not None
+
+        kv_nope = self.kv_b_proj(kv_c_normed)[0].view(\
+            -1, self.num_heads, self.qk_nope_head_dim + self.v_head_dim)
+        k_nope, v = kv_nope\
+            .split([self.qk_nope_head_dim, self.v_head_dim], dim=-1)
+
+        k = torch.cat((k_nope, k_pe.expand((*k_nope.shape[:-1], -1))), dim=-1)
+
+        # For MLA the v head dim is smaller than qk head dim so we pad out
+        # v with 0s to match the qk head dim
+        v_padded = torch.nn.functional.pad(v, [0, q.shape[-1] - v.shape[-1]],
+                                           value=0)
+
+        output = torch.empty_like(q)
+        ipex_ops.varlen_attention(
+            query=q,
+            key=k,
+            value=v_padded,
+            out=output,
+            seqlen_q=prefill_metadata.prefill_query_start_loc,
+            seqlen_k=prefill_metadata.prefill_query_start_loc,
+            max_seqlen_q=prefill_metadata.max_query_len,
+            max_seqlen_k=prefill_metadata.max_query_len,
+            pdropout=0.0,
+            softmax_scale=self.scale,
+            zero_tensors=False,
+            is_causal=True,
+            return_softmax=False,
+            gen_=None,
+            logits_soft_cap=0.0,
+            window_size_left=-1,
+            window_size_right=-1,
+            alibi_slopes=None,
+        )
+
+        # remove padding
+        output = output.view(-1, self.num_heads,
+                             q.shape[-1])[..., :v.shape[-1]]
+        return output.reshape(-1, self.num_heads * v.shape[-1])
+
+    def _forward_decode(
+            self,
+            q_nope: torch.Tensor,
+            q_pe: torch.Tensor,
+            kv_c_and_k_pe_cache: torch.Tensor,
+            attn_metadata: CPUMLAMetadata,  # type: ignore[override]
+    ) -> torch.Tensor:
+        assert kv_c_and_k_pe_cache.numel() > 0
+
+        decode_meta = attn_metadata.decode_metadata
+        assert decode_meta is not None
+
+        q = torch.cat([q_nope, q_pe], dim=-1)
+        o = q.new_empty(q.shape[0], self.num_heads, self.kv_lora_rank)
+
+        # Run MQA
+        ops.mla_decode_kvcache_cpu(o, q, kv_c_and_k_pe_cache, self.scale,
+                                   decode_meta.block_tables,
+                                   decode_meta.seq_lens_tensor)
+        return self._v_up_proj(o)

vllm/attention/backends/ipex_attn.py

@@ -0,0 +1,403 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+""" Attention layer with torch scaled_dot_product_attention
+    and PagedAttention."""
+from dataclasses import dataclass
+from typing import Any, Dict, List, Optional, Tuple, Type
+
+import torch
+
+from vllm._ipex_ops import ipex_ops
+from vllm.attention.backends.abstract import (AttentionBackend, AttentionImpl,
+                                              AttentionLayer,
+                                              AttentionMetadata, AttentionType,
+                                              is_quantized_kv_cache)
+from vllm.attention.backends.utils import CommonAttentionState
+from vllm.attention.ops.paged_attn import (PagedAttention,
+                                           PagedAttentionMetadata)
+from vllm.logger import init_logger
+
+logger = init_logger(__name__)
+
+_PARTITION_SIZE = 512
+
+
+class IpexAttnBackend(AttentionBackend):
+
+    @staticmethod
+    def get_name() -> str:
+        return "IPEX"
+
+    @staticmethod
+    def get_impl_cls() -> Type["IpexAttnBackendImpl"]:
+        return IpexAttnBackendImpl
+
+    @staticmethod
+    def get_metadata_cls() -> Type["IpexAttnMetadata"]:
+        return IpexAttnMetadata
+
+    @staticmethod
+    def get_state_cls() -> Type["CommonAttentionState"]:
+        return CommonAttentionState
+
+    @staticmethod
+    def get_kv_cache_shape(
+        num_blocks: int,
+        block_size: int,
+        num_kv_heads: int,
+        head_size: int,
+    ) -> Tuple[int, ...]:
+        return PagedAttention.get_kv_cache_shape(num_blocks, block_size,
+                                                 num_kv_heads, head_size)
+
+    @staticmethod
+    def swap_blocks(
+        src_kv_cache: torch.Tensor,
+        dst_kv_cache: torch.Tensor,
+        src_to_dst: torch.Tensor,
+    ) -> None:
+        from vllm._ipex_ops import ipex_ops as ops
+        ops.swap_blocks(src_kv_cache, dst_kv_cache, src_to_dst)
+
+    @staticmethod
+    def copy_blocks(
+        kv_caches: List[torch.Tensor],
+        src_to_dists: torch.Tensor,
+    ) -> None:
+        from vllm._ipex_ops import ipex_ops as ops
+        key_caches = [kv_cache[0] for kv_cache in kv_caches]
+        value_caches = [kv_cache[1] for kv_cache in kv_caches]
+        ops.copy_blocks(key_caches, value_caches, src_to_dists)
+
+
+@dataclass
+class IpexAttnMetadata(AttentionMetadata, PagedAttentionMetadata):
+    """Metadata for IpexAttnBackend.
+    """
+    # Currently, input sequences can only contain all prompts
+    # or all decoding. True if all sequences are prompts.
+    is_prompt: bool
+    slot_mapping: torch.Tensor
+    seq_lens: Optional[List[int]]
+    seqlen_q: Optional[torch.Tensor]
+    max_seqlen: Optional[int]
+
+    def __post_init__(self):
+        # Set during the execution of the first attention op.
+        # It is a list because it is needed to set per prompt
+        # when alibi slopes is used. It is because of the limitation
+        # from xformer API.
+        # will not appear in the __repr__ and __init__
+        self.attn_bias: Optional[List[torch.Tensor]] = None
+
+    @property
+    def prefill_metadata(self) -> Optional["IpexAttnMetadata"]:
+        # Currently chunked prefill is not supported
+        if self.num_decode_tokens == 0:
+            assert self.num_prefills > 0
+            return self
+
+        return None
+
+    @property
+    def decode_metadata(self) -> Optional["IpexAttnMetadata"]:
+        # Currently chunked prefill is not supported
+        if self.num_prefills > 0:
+            assert self.num_decode_tokens == 0
+            return None
+
+        return self
+
+
+class IpexAttnBackendImpl(AttentionImpl[IpexAttnMetadata]):
+
+    def __init__(
+        self,
+        num_heads: int,
+        head_size: int,
+        scale: float,
+        num_kv_heads: int,
+        alibi_slopes: Optional[List[float]],
+        sliding_window: Optional[int],
+        kv_cache_dtype: str,
+        blocksparse_params: Optional[Dict[str, Any]] = None,
+        logits_soft_cap: Optional[float] = None,
+        attn_type: str = AttentionType.DECODER,
+        kv_sharing_target_layer_name: Optional[str] = None,
+        use_irope: bool = False,
+    ) -> None:
+        if kv_sharing_target_layer_name is not None:
+            raise NotImplementedError("KV sharing is not supported in V0.")
+        if use_irope:
+            logger.warning_once(
+                "Using irope in Ipex is not supported yet, it will fall"
+                " back to global attention for long context.")
+        if blocksparse_params is not None:
+            raise ValueError(
+                "IPEX backend does not support block-sparse attention.")
+        self.num_heads = num_heads
+        self.head_size = head_size
+        self.scale = float(scale)
+        self.num_kv_heads = num_kv_heads
+        if alibi_slopes is not None:
+            alibi_slopes = torch.tensor(alibi_slopes, dtype=torch.float32)
+        self.alibi_slopes = alibi_slopes
+        self.sliding_window = sliding_window
+        self.kv_cache_dtype = kv_cache_dtype
+
+        self.num_queries_per_kv = self.num_heads // self.num_kv_heads
+        self.need_mask = (self.sliding_window is not None)
+        if logits_soft_cap is None:
+            logits_soft_cap = -1
+        self.logits_soft_cap = logits_soft_cap
+
+        supported_head_sizes = PagedAttention.get_supported_head_sizes()
+        if head_size not in supported_head_sizes:
+            raise ValueError(
+                f"Head size {head_size} is not supported by PagedAttention. "
+                f"Supported head sizes are: {supported_head_sizes}.")
+        if is_quantized_kv_cache(kv_cache_dtype):
+            raise NotImplementedError(
+                "IPEX backend does not support FP8 KV cache. "
+                "Please use xFormers backend instead.")
+        if attn_type != AttentionType.DECODER:
+            raise NotImplementedError("Encoder self-attention and "
+                                      "encoder/decoder cross-attention "
+                                      "are not implemented for "
+                                      "IpexAttnBackendImpl")
+
+    def split_kv_cache(
+        self,
+        kv_cache: torch.Tensor,
+        num_kv_heads: int,
+        head_size: int,
+    ) -> Tuple[torch.Tensor, torch.Tensor]:
+        x = 1
+        num_blocks = kv_cache.shape[1]
+
+        key_cache = kv_cache[0]
+        key_cache = key_cache.view(num_blocks, num_kv_heads, head_size // x,
+                                   -1, x)
+        value_cache = kv_cache[1]
+        value_cache = value_cache.view(num_blocks, num_kv_heads, head_size, -1)
+        return key_cache, value_cache
+
+    def forward(
+        self,
+        layer: AttentionLayer,
+        query: torch.Tensor,
+        key: torch.Tensor,
+        value: torch.Tensor,
+        kv_cache: torch.Tensor,
+        attn_metadata: IpexAttnMetadata,  # type: ignore
+        output: Optional[torch.Tensor] = None,
+        output_scale: Optional[torch.Tensor] = None,
+    ) -> torch.Tensor:
+        """Forward pass with IPEX varlen_attention and PagedAttention.
+
+        Args:
+            query: shape = [num_tokens, num_heads * head_size]
+            key: shape = [num_tokens, num_kv_heads * head_size]
+            value: shape = [num_tokens, num_kv_heads * head_size]
+            kv_cache = [2, num_blocks, block_size * num_kv_heads * head_size]
+                NOTE: kv_cache will be an empty tensor with shape [0]
+                for profiling run.
+            attn_metadata: Metadata for attention.
+        Returns:
+            shape = [num_tokens, num_heads * head_size]
+        """
+        if output_scale is not None:
+            raise NotImplementedError(
+                "fused output quantization is not yet supported"
+                " for IpexAttentionImpl")
+
+        assert layer._k_scale_float == 1.0 and layer._v_scale_float == 1.0
+        num_tokens, hidden_size = query.shape
+        # Reshape the query, key, and value tensors.
+        query = query.view(-1, self.num_heads, self.head_size)
+        key = key.view(-1, self.num_kv_heads, self.head_size)
+        value = value.view(-1, self.num_kv_heads, self.head_size)
+
+        if kv_cache.numel() > 0:
+            key_cache, value_cache = self.split_kv_cache(
+                kv_cache, self.num_kv_heads, self.head_size)
+            ipex_ops.reshape_and_cache(
+                key,
+                value,
+                key_cache,
+                value_cache,
+                attn_metadata.slot_mapping.flatten(),
+                self.kv_cache_dtype,
+                layer._k_scale_float,
+                layer._v_scale_float,
+            )
+
+        if attn_metadata.is_prompt:
+            assert attn_metadata.seq_lens is not None
+            if (kv_cache.numel() == 0
+                    or attn_metadata.block_tables.numel() == 0):
+                if self.num_kv_heads != self.num_heads:
+                    key = key.repeat_interleave(self.num_queries_per_kv, dim=1)
+                    value = value.repeat_interleave(self.num_queries_per_kv,
+                                                    dim=1)
+
+                if attn_metadata.attn_bias is None:
+                    if self.sliding_window is not None:
+                        att_masks = _make_sliding_window_bias(
+                            attn_metadata.seq_lens, self.sliding_window,
+                            query.dtype)  # type: ignore
+                    else:
+                        att_masks = _make_sliding_window_bias(
+                            attn_metadata.seq_lens, None, dtype=query.dtype)
+                    attn_metadata.attn_bias = att_masks
+
+                output = torch.empty(
+                    (num_tokens, self.num_heads, self.head_size),
+                    dtype=query.dtype,
+                    device=query.device)
+                ipex_ops.varlen_attention(
+                    query,
+                    key,
+                    value,
+                    output,
+                    attn_metadata.seqlen_q,
+                    attn_metadata.seqlen_q,
+                    self.alibi_slopes,
+                    attn_metadata.max_seqlen,
+                    attn_metadata.max_seqlen,
+                    pdropout=0.0,
+                    softmax_scale=self.scale,
+                    zero_tensors=False,
+                    is_causal=True,
+                    return_softmax=False,
+                    gen_=None,
+                    window_size_left=-1,
+                    window_size_right=-1,
+                    logits_soft_cap=self.logits_soft_cap,
+                )
+            else:
+                # prefix-enabled attention
+                raise RuntimeError(
+                    "IPEX backend doesn't support prefix decoding.")
+
+        else:
+            # Decoding run.
+            max_seq_len = attn_metadata.max_decode_seq_len
+            output = torch.empty_like(query)
+            block_size = value_cache.shape[3]
+            num_seqs, num_heads, head_size = query.shape
+            max_num_partitions = ((max_seq_len + _PARTITION_SIZE - 1) //
+                                  _PARTITION_SIZE)
+            # NOTE(woosuk): We use a simple heuristic to decide whether to use
+            # PagedAttention V1 or V2. If the number of partitions is 1, we use
+            # V1 to avoid the overhead of reduction. Also, if the number of
+            # sequences or heads is large, we use V1 since there is enough work
+            # to parallelize.
+            # TODO(woosuk): Tune this heuristic.
+            # For context len > 8192, use V2 kernel to avoid shared memory
+            # shortage.
+            use_v1 = (max_seq_len <= 8192 and
+                      (max_num_partitions == 1 or num_seqs * num_heads > 512))
+            if use_v1:
+                # Run PagedAttention V1.
+                ipex_ops.paged_attention_v1(
+                    output,
+                    query,
+                    key_cache,
+                    value_cache,
+                    self.num_kv_heads,
+                    self.scale,
+                    attn_metadata.block_tables,
+                    attn_metadata.seq_lens_tensor,
+                    block_size,
+                    max_seq_len,
+                    self.alibi_slopes,
+                    self.kv_cache_dtype,
+                    layer._k_scale_float,
+                    layer._v_scale_float,
+                )
+            else:
+                # Run PagedAttention V2.
+                assert _PARTITION_SIZE % block_size == 0
+                tmp_output = torch.empty(
+                    size=(num_seqs, num_heads, max_num_partitions, head_size),
+                    dtype=output.dtype,
+                    device=output.device,
+                )
+                exp_sums = torch.empty(
+                    size=(num_seqs, num_heads, max_num_partitions),
+                    dtype=torch.float32,
+                    device=output.device,
+                )
+                max_logits = torch.empty_like(exp_sums)
+                ipex_ops.paged_attention_v2(
+                    output,
+                    exp_sums,
+                    max_logits,
+                    tmp_output,
+                    query,
+                    key_cache,
+                    value_cache,
+                    self.num_kv_heads,
+                    self.scale,
+                    attn_metadata.block_tables,
+                    attn_metadata.seq_lens_tensor,
+                    block_size,
+                    max_seq_len,
+                    self.alibi_slopes,
+                    self.kv_cache_dtype,
+                    layer._k_scale_float,
+                    layer._v_scale_float,
+                )
+
+            # Reshape the output tensor.
+        return output.view(-1, self.num_heads * self.head_size)
+
+
+def _make_alibi_bias(
+    alibi_slopes: torch.Tensor,
+    dtype: torch.dtype,
+    seq_lens: List[int],
+) -> List[torch.Tensor]:
+    attn_biases = []
+    for seq_len in seq_lens:
+        bias = torch.arange(seq_len, dtype=dtype, device=alibi_slopes.device)
+        # NOTE(zhuohan): HF uses
+        #     `bias = bias[None, :].repeat(seq_len, 1)`
+        # here. We find that both biases give the same results, but
+        # the bias below more accurately follows the original ALiBi
+        # paper.
+        bias = bias[None, :] - bias[:, None]
+
+        num_heads = alibi_slopes.shape[0]
+        bias = bias[None, :].repeat((num_heads, 1, 1))
+        bias.mul_(alibi_slopes[:, None, None])
+        inf_mask = torch.empty(
+            (1, seq_len, seq_len),
+            dtype=bias.dtype,
+            device=alibi_slopes.device).fill_(-torch.inf).triu_(diagonal=1)
+        attn_biases.append((bias + inf_mask).to(dtype))
+
+    return attn_biases
+
+
+def _make_sliding_window_bias(
+    seq_lens: List[int],
+    window_size: Optional[int],
+    dtype: torch.dtype,
+) -> List[torch.Tensor]:
+    attn_biases = []
+    for seq_len in seq_lens:
+        tensor = torch.full(
+            (1, seq_len, seq_len),
+            dtype=dtype,
+            fill_value=1,
+        )
+        shift = 0
+        mask = torch.tril(tensor, diagonal=shift).to(dtype)  # type: ignore
+        if window_size is not None:
+            mask = torch.triu(mask, diagonal=shift - window_size + 1)
+        mask = torch.log(mask)
+        attn_biases.append(mask.to(dtype))
+
+    return attn_biases

vllm/attention/backends/pallas.py

@@ -0,0 +1,356 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+from dataclasses import dataclass
+from typing import Any, Dict, List, Optional, Tuple, Type
+
+import torch
+import torch_xla.experimental.custom_kernel  # Required to register custom ops.
+
+from vllm.attention.backends.abstract import (AttentionBackend, AttentionImpl,
+                                              AttentionLayer,
+                                              AttentionMetadata, AttentionType,
+                                              is_quantized_kv_cache)
+from vllm.attention.backends.utils import CommonAttentionState
+from vllm.logger import init_logger
+
+logger = init_logger(__name__)
+
+
+class PallasAttentionBackend(AttentionBackend):
+
+    @staticmethod
+    def get_name() -> str:
+        return "PALLAS"
+
+    @staticmethod
+    def get_impl_cls() -> Type["PallasAttentionBackendImpl"]:
+        return PallasAttentionBackendImpl
+
+    @staticmethod
+    def get_metadata_cls() -> Type["PallasMetadata"]:
+        return PallasMetadata
+
+    @staticmethod
+    def get_state_cls() -> Type["CommonAttentionState"]:
+        return CommonAttentionState
+
+    @staticmethod
+    def get_kv_cache_shape(
+        num_blocks: int,
+        block_size: int,
+        num_kv_heads: int,
+        head_size: int,
+    ) -> Tuple[int, ...]:
+        return (num_kv_heads, num_blocks, block_size, head_size)
+
+    @staticmethod
+    def swap_blocks(
+        src_kv_cache: torch.Tensor,
+        dst_kv_cache: torch.Tensor,
+        src_to_dst: torch.Tensor,
+    ) -> None:
+        raise RuntimeError("swap_blocks is not used for the TPU backend.")
+
+    @torch.compile(backend="openxla")
+    @staticmethod
+    def copy_blocks(
+        kv_caches: List[Tuple[torch.Tensor, torch.Tensor]],
+        src_to_dists: Tuple[torch.Tensor, torch.Tensor],
+    ) -> None:
+        src_indices, dst_indices = src_to_dists
+        for k_cache, v_cache in kv_caches:
+            torch.ops.xla.dynamo_set_buffer_donor_(k_cache, True)
+            k_cache[:, dst_indices] = k_cache[:, src_indices]
+            torch.ops.xla.dynamo_set_buffer_donor_(v_cache, True)
+            v_cache[:, dst_indices] = v_cache[:, src_indices]
+
+
+@dataclass
+class PallasMetadata(AttentionMetadata):
+
+    # Currently, input sequences can only contain all prefills
+    # or all decoding.
+    block_tables: Optional[torch.Tensor] = None
+    context_lens: Optional[torch.Tensor] = None
+    effective_query_lens: Optional[torch.Tensor] = None
+
+    @property
+    def prefill_metadata(self) -> Optional["PallasMetadata"]:
+        if self.num_prefills == 0:
+            return None
+
+        assert self.num_decode_tokens == 0
+        return self
+
+    @property
+    def decode_metadata(self) -> Optional["PallasMetadata"]:
+        if self.num_decode_tokens == 0:
+            return None
+
+        assert self.num_prefills == 0
+        assert self.num_prefill_tokens == 0
+        assert self.block_tables is not None
+        assert self.context_lens is not None
+        return self
+
+
+class PallasAttentionBackendImpl(AttentionImpl):
+
+    def __init__(
+        self,
+        num_heads: int,
+        head_size: int,
+        scale: float,
+        num_kv_heads: int,
+        alibi_slopes: Optional[List[float]],
+        sliding_window: Optional[int],
+        kv_cache_dtype: str,
+        blocksparse_params: Optional[Dict[str, Any]] = None,
+        logits_soft_cap: Optional[float] = None,
+        attn_type: str = AttentionType.DECODER,
+        kv_sharing_target_layer_name: Optional[str] = None,
+        use_irope: bool = False,
+    ) -> None:
+        if kv_sharing_target_layer_name is not None:
+            raise NotImplementedError("KV sharing is not supported in V0.")
+        if use_irope:
+            logger.warning_once(
+                "Using irope in Pallas is not supported yet, it will fall back "
+                "to global attention for long context.")
+        self.num_heads = num_heads
+        self.head_size = head_size
+        self.scale = float(scale)
+        self.num_kv_heads = num_kv_heads
+
+        self.num_queries_per_kv = self.num_heads // self.num_kv_heads
+        self.logits_soft_cap = logits_soft_cap
+        if head_size % 128 != 0:
+            raise NotImplementedError(
+                f"Head size must be a multiple of 128, found {head_size}.")
+        if alibi_slopes is not None:
+            raise NotImplementedError("Alibi slopes is not supported.")
+        if sliding_window is not None:
+            raise NotImplementedError("Sliding window is not supported.")
+        if is_quantized_kv_cache(kv_cache_dtype):
+            raise NotImplementedError("FP8 KV cache dtype is not supported.")
+        if blocksparse_params is not None:
+            raise NotImplementedError("Blocksparse is not supported.")
+
+        if torch_xla.tpu.version() < 4:
+            raise NotImplementedError("TPU version must be 4 or higher.")
+
+        self.megacore_mode = None
+        tpu_env = torch_xla.tpu.get_tpu_env()
+        tpu_type = (tpu_env.get("ACCELERATOR_TYPE", None)
+                    or tpu_env.get("TYPE", None)
+                    or tpu_env.get("TPU_ACCELERATOR_TYPE", None))
+        assert tpu_type is not None
+        tpu_type = tpu_type.lower()
+
+        if (("lite" not in tpu_type) and ("v6" not in tpu_type)):
+            if self.num_kv_heads % 2 == 0:
+                self.megacore_mode = "kv_head"
+            else:
+                # NOTE(woosuk): If the batch size is not a multiple of 2, the
+                # megacore mode will be None.
+                self.megacore_mode = "batch"
+
+        if attn_type != AttentionType.DECODER:
+            raise NotImplementedError("Encoder self-attention and "
+                                      "encoder/decoder cross-attention "
+                                      "are not implemented for "
+                                      "PallasAttentionBackendImpl")
+
+    def forward(
+        self,
+        layer: AttentionLayer,
+        query: torch.Tensor,
+        key: torch.Tensor,
+        value: torch.Tensor,
+        kv_cache: Tuple[torch.Tensor, torch.Tensor],
+        attn_metadata: PallasMetadata,
+        output: Optional[torch.Tensor] = None,
+        output_scale: Optional[torch.Tensor] = None,
+    ) -> torch.Tensor:
+        """Forward pass with Pallas attention.
+
+        Args:
+            query: shape = [batch_size, seq_len, num_heads * head_size]
+            key: shape = [batch_size, seq_len, num_kv_heads * head_size]
+            value: shape = [batch_size, seq_len, num_kv_heads * head_size]
+            kv_cache[0] = [num_kv_heads, num_blocks, block_size, head_size]
+            kv_cache[1] = [num_kv_heads, num_blocks, block_size, head_size]
+                NOTE: kv_cache[0] and kv_cache[1] will be an empty tensor 
+                with shape [0] for profiling run.
+            attn_metadata: Metadata for attention.
+        Returns:
+            shape = [batch_size, seq_len, num_heads * head_size]
+        """
+        if output_scale is not None:
+            raise NotImplementedError(
+                "fused output quantization is not yet supported"
+                " for PallasAttentionImpl")
+
+        assert layer._k_scale_float == 1.0 and layer._v_scale_float == 1.0
+        batch_size, seq_len, hidden_size = query.shape
+        query = query.view(batch_size, seq_len, self.num_heads, self.head_size)
+        key = key.view(batch_size, seq_len, self.num_kv_heads, self.head_size)
+        value = value.view(batch_size, seq_len, self.num_kv_heads,
+                           self.head_size)
+
+        if kv_cache[0].numel() > 0:
+            slot_mapping = attn_metadata.slot_mapping
+            key_cache, value_cache = kv_cache
+            write_to_kv_cache(key, value, key_cache, value_cache, slot_mapping)
+
+        query = query * self.scale
+        if attn_metadata.num_prefills > 0:
+            if attn_metadata.block_tables is None:
+                # Prefill without paged KV cache.
+                assert seq_len % 16 == 0, (
+                    "Pallas FlashAttention kernel requires seq_len to be a "
+                    f"multiple of 16 but got {seq_len}")
+
+                # Handle GQA/MQA.
+                if self.num_kv_heads != self.num_heads:
+                    key = key.repeat_interleave(self.num_queries_per_kv,
+                                                dim=-2)
+                    key = key.view(batch_size, seq_len, self.num_heads,
+                                   self.head_size)
+                    value = value.repeat_interleave(self.num_queries_per_kv,
+                                                    dim=-2)
+                    value = value.view(batch_size, seq_len, self.num_heads,
+                                       self.head_size)
+                # FlashAttention kernel requires the input shape to be
+                # [batch_size, num_heads, seq_len, d_model]
+                # while the input is [batch_size, seq_len, num_heads, d_model].
+                # Permute the input to match the required format.
+                output = torch.ops.xla.flash_attention(
+                    query.permute(0, 2, 1, 3),
+                    key.permute(0, 2, 1, 3),
+                    value.permute(0, 2, 1, 3),
+                    True,
+                )
+                output = output.permute(0, 2, 1, 3)
+            else:
+                # Prefill with paged KV cache.
+                # TODO(woosuk): Tune the below knobs.
+                num_kv_pages_per_compute_block = 16
+                num_queries_per_compute_block = 16
+                assert seq_len % num_queries_per_compute_block == 0
+                output = torch.ops.xla.multi_queries_paged_attention(
+                    query,
+                    key_cache,
+                    value_cache,
+                    attn_metadata.context_lens,
+                    attn_metadata.block_tables,
+                    attn_metadata.effective_query_lens,
+                    num_kv_pages_per_compute_block,
+                    num_queries_per_compute_block,
+                    use_kernel=True,
+                    attn_logits_soft_cap=self.logits_soft_cap,
+                )
+        else:
+            # Decoding run.
+            assert kv_cache[0].numel() > 0
+            query = query.squeeze(dim=1)
+            pages_per_compute_block = 16  # TODO(woosuk): Tune this value.
+
+            assert attn_metadata.block_tables is not None
+            assert attn_metadata.context_lens is not None
+            # NOTE(woosuk): The PagedAttention Pallas kernel stores the entire
+            # block table in SMEM. Therefore, if the block table is too large,
+            # the kernel compilation will fail. To avoid this, we split the
+            # batch dimension into smaller chunks and run the kernel multiple
+            # times.
+            MAX_SMEM_USAGE = 512 * 1024
+            size_per_seq = 4 * attn_metadata.block_tables.shape[1]
+            max_num_seq = MAX_SMEM_USAGE // size_per_seq
+
+            if batch_size <= max_num_seq:
+                output = paged_attention(
+                    query,
+                    key_cache,
+                    value_cache,
+                    attn_metadata.context_lens,
+                    attn_metadata.block_tables,
+                    pages_per_compute_block,
+                    self.megacore_mode,
+                    attn_logits_soft_cap=self.logits_soft_cap,
+                )
+            else:
+                chunk_size = max_num_seq
+                # Make sure the chunk size is a multiple of 2.
+                chunk_size = chunk_size // 2 * 2
+                num_chunks = (batch_size + chunk_size - 1) // chunk_size
+
+                output = torch.empty_like(query)
+                for chunk_idx in range(num_chunks):
+                    chunk_start = chunk_idx * chunk_size
+                    chunk_end = chunk_start + chunk_size
+                    # NOTE(woosuk): We skip this line because it causes Dynamo
+                    # compilation error. Instead, we rely on the slice operation
+                    # to handle the out-of-bound case.
+                    # chunk_end = min(chunk_end, batch_size)
+                    chunk_output = paged_attention(
+                        query[chunk_start:chunk_end],
+                        key_cache,
+                        value_cache,
+                        attn_metadata.context_lens[chunk_start:chunk_end],
+                        attn_metadata.block_tables[chunk_start:chunk_end],
+                        pages_per_compute_block,
+                        self.megacore_mode,
+                        attn_logits_soft_cap=self.logits_soft_cap,
+                    )
+                    output[chunk_start:chunk_end] = chunk_output
+
+        # Reshape the output tensor.
+        return output.reshape(batch_size, seq_len, hidden_size)
+
+
+def write_to_kv_cache(
+    key: torch.Tensor,
+    value: torch.Tensor,
+    key_cache: torch.Tensor,
+    value_cache: torch.Tensor,
+    slot_mapping: torch.Tensor,
+) -> None:
+    torch.ops.xla.dynamo_set_buffer_donor_(key_cache, True)
+    torch.ops.xla.dynamo_set_buffer_donor_(value_cache, True)
+
+    key = key.flatten(0, 2)
+    value = value.flatten(0, 2)
+    key_cache = key_cache.flatten(0, 2)
+    value_cache = value_cache.flatten(0, 2)
+    key_cache.index_copy_(0, slot_mapping, key)
+    value_cache.index_copy_(0, slot_mapping, value)
+
+
+def paged_attention(
+    query: torch.Tensor,
+    key_cache: torch.Tensor,
+    value_cache: torch.Tensor,
+    context_lens: torch.Tensor,
+    block_tables: torch.Tensor,
+    pages_per_compute_block: int,
+    megacore_mode: Optional[str],
+    *,
+    attn_logits_soft_cap: Optional[float],
+) -> torch.Tensor:
+    batch_size = query.shape[0]
+    if megacore_mode == "batch" and batch_size % 2 != 0:
+        megacore_mode = None
+    else:
+        megacore_mode = megacore_mode
+
+    return torch.ops.xla.paged_attention(
+        query,
+        key_cache,
+        value_cache,
+        context_lens,
+        block_tables,
+        pages_per_compute_block,
+        megacore_mode=megacore_mode,
+        attn_logits_soft_cap=attn_logits_soft_cap,
+    )

vllm/attention/backends/torch_sdpa.py

@@ -3,24 +3,78 @@
 """ Attention layer with torch scaled_dot_product_attention
     and PagedAttention."""
 from dataclasses import dataclass
-from typing import Any, Dict, List, Optional
+from typing import Any, Dict, List, Optional, Tuple, Type
 
 import torch
 from torch.nn.functional import scaled_dot_product_attention
 
 # yapf conflicts with isort for this block
 # yapf: disable
-from vllm.attention.backends.abstract import (AttentionImpl, AttentionLayer,
+from vllm.attention.backends.abstract import (AttentionBackend, AttentionImpl,
-                                              AttentionMetadata, AttentionType,
+                                              AttentionLayer,
+                                              AttentionMetadata,
+                                              AttentionMetadataBuilder,
+                                              AttentionType,
                                               is_quantized_kv_cache)
 # yapf: enable
+from vllm.attention.backends.utils import CommonAttentionState
 from vllm.attention.ops.ipex_attn import PagedAttention, _use_ipex
 from vllm.attention.ops.paged_attn import PagedAttentionMetadata
 from vllm.logger import init_logger
+from vllm.utils import make_tensor_with_pad
+from vllm.worker.cpu_model_runner import ModelInputForCPUBuilder
 
 logger = init_logger(__name__)
 
 
+class TorchSDPABackend(AttentionBackend):
+
+    @staticmethod
+    def get_name() -> str:
+        return "TORCH_SDPA"
+
+    @staticmethod
+    def get_impl_cls() -> Type["TorchSDPABackendImpl"]:
+        return TorchSDPABackendImpl
+
+    @staticmethod
+    def get_metadata_cls() -> Type["AttentionMetadata"]:
+        return TorchSDPAMetadata
+
+    @staticmethod
+    def get_state_cls() -> Type["CommonAttentionState"]:
+        return CommonAttentionState
+
+    @staticmethod
+    def get_builder_cls() -> Type["TorchSDPAMetadataBuilder"]:
+        return TorchSDPAMetadataBuilder
+
+    @staticmethod
+    def get_kv_cache_shape(
+        num_blocks: int,
+        block_size: int,
+        num_kv_heads: int,
+        head_size: int,
+    ) -> Tuple[int, ...]:
+        return PagedAttention.get_kv_cache_shape(num_blocks, block_size,
+                                                 num_kv_heads, head_size)
+
+    @staticmethod
+    def swap_blocks(
+        src_kv_cache: torch.Tensor,
+        dst_kv_cache: torch.Tensor,
+        src_to_dst: torch.Tensor,
+    ) -> None:
+        raise NotImplementedError("Swap is not supported in TorchSDPABackend.")
+
+    @staticmethod
+    def copy_blocks(
+        kv_caches: List[torch.Tensor],
+        src_to_dists: torch.Tensor,
+    ) -> None:
+        PagedAttention.copy_blocks(kv_caches, src_to_dists)
+
+
 @dataclass
 class TorchSDPAMetadata(AttentionMetadata, PagedAttentionMetadata):
     """Metadata for TorchSDPABackend.
@@ -233,6 +287,113 @@ class TorchSDPAMetadata(AttentionMetadata, PagedAttentionMetadata):
             raise AttributeError(f"Invalid attention type {str(attn_type)}")
 
 
+class TorchSDPAMetadataBuilder(AttentionMetadataBuilder[TorchSDPAMetadata]):
+
+    def __init__(self, input_builder: ModelInputForCPUBuilder) -> None:
+        self.chunked_prefill = input_builder.chunked_prefill
+        self.input_builder = input_builder
+
+    def prepare(self):
+        self.input_data = self.input_builder.input_data
+
+    def build(self, seq_lens: List[int], query_lens: List[int],
+              cuda_graph_pad_size: int, batch_size: int) -> TorchSDPAMetadata:
+        input_data = self.input_data
+        prefill_seq_lens = seq_lens[0:input_data.num_prefills]
+        prefill_query_lens = query_lens[0:input_data.num_prefills]
+        slot_mapping = torch.tensor(input_data.slot_mapping,
+                                    dtype=torch.long,
+                                    device="cpu")
+
+        # For chunked-prefill
+        if self.chunked_prefill and input_data.num_prefill_tokens != 0:
+            prefill_block_tables = make_tensor_with_pad(
+                self.input_data.prefill_block_tables,
+                pad=0,
+                dtype=torch.int32,
+                device="cpu",
+            )
+            query_lens_tensor = torch.tensor(prefill_query_lens,
+                                             dtype=torch.int32,
+                                             device="cpu")
+            kv_lens_tensor = torch.tensor(prefill_seq_lens,
+                                          dtype=torch.int32,
+                                          device="cpu")
+            query_start_loc = torch.zeros(input_data.num_prefills + 1,
+                                          dtype=torch.int32,
+                                          device="cpu")
+            kv_start_loc = torch.zeros(input_data.num_prefills + 1,
+                                       dtype=torch.int32,
+                                       device="cpu")
+            torch.cumsum(query_lens_tensor,
+                         dim=0,
+                         dtype=torch.int32,
+                         out=query_start_loc[1:])
+            torch.cumsum(kv_lens_tensor,
+                         dim=0,
+                         dtype=torch.int32,
+                         out=kv_start_loc[1:])
+            max_query_len = max(prefill_query_lens)
+            max_kv_len = max(prefill_seq_lens)
+        else:
+            prefill_block_tables = None
+            query_start_loc = None
+            kv_start_loc = None
+            max_query_len = None
+            max_kv_len = None
+
+        # For paged attention
+        if input_data.num_decode_tokens != 0:
+            seq_lens_tensor = torch.tensor(
+                input_data.seq_lens[input_data.num_prefills:],
+                dtype=torch.int32,
+                device="cpu",
+            )
+            block_tables = make_tensor_with_pad(
+                self.input_data.decode_block_tables,
+                pad=0,
+                dtype=torch.int32,
+                device="cpu",
+            )
+        else:
+            block_tables = torch.tensor([])
+            seq_lens_tensor = torch.tensor(
+                input_data.seq_lens[:input_data.num_prefills],
+                dtype=torch.int32,
+                device="cpu",
+            )
+
+        # For multi-modal models
+        placeholder_index_maps = None
+        if len(input_data.multi_modal_inputs_list) != 0:
+            placeholder_index_maps = {
+                modality: placeholder_map.index_map()
+                for modality, placeholder_map in
+                input_data.multi_modal_placeholder_maps.items()
+            }
+
+        attn_metadata = TorchSDPAMetadata(
+            chunked_prefill=self.chunked_prefill,
+            seq_lens=prefill_seq_lens,
+            seq_lens_tensor=seq_lens_tensor,
+            max_query_len=max_query_len,
+            max_kv_len=max_kv_len,
+            prefill_query_start_loc=query_start_loc,
+            kv_start_loc=kv_start_loc,
+            max_decode_seq_len=input_data.max_decode_seq_len,
+            num_prefills=input_data.num_prefills,
+            num_prefill_tokens=input_data.num_prefill_tokens,
+            num_decode_tokens=input_data.num_decode_tokens,
+            block_tables=block_tables,
+            prefill_block_tables=prefill_block_tables,
+            slot_mapping=slot_mapping,
+            multi_modal_placeholder_index_maps=placeholder_index_maps,
+            enable_kv_scales_calculation=False,
+        )
+
+        return attn_metadata
+
+
 class TorchSDPABackendImpl(AttentionImpl[TorchSDPAMetadata]):
 
     def __init__(

vllm/platforms/cpu.py

@@ -64,11 +64,13 @@ class CpuPlatform(Platform):
         if selected_backend and selected_backend != _Backend.TORCH_SDPA:
             logger.info("Cannot use %s backend on CPU.", selected_backend)
         if use_mla:
-            raise NotImplementedError("MLA is not supported on CPU.")
+            logger.info("Using CPU MLA backend.")
+            return "vllm.attention.backends.cpu_mla.CPUMLABackend"
         logger.info("Using Torch SDPA backend.")
-        if not use_v1:
+        if use_v1:
-            raise ValueError("CPU backend only supports V1.")
+            return "vllm.v1.attention.backends.cpu_attn.TorchSDPABackend"
-        return "vllm.v1.attention.backends.cpu_attn.TorchSDPABackend"
+        else:
+            return "vllm.attention.backends.torch_sdpa.TorchSDPABackend"
 
     @classmethod
     def get_device_total_memory(cls, device_id: int = 0) -> int:
@@ -145,14 +147,26 @@ class CpuPlatform(Platform):
                            parallel_config.distributed_executor_backend)
             parallel_config.distributed_executor_backend = "mp"
         if parallel_config.worker_cls == "auto":
-            parallel_config.worker_cls = "vllm.v1.worker.cpu_worker.CPUWorker"
+            if vllm_config.speculative_config:
+                parallel_config.worker_cls = \
+                    "vllm.spec_decode.spec_decode_worker.create_spec_worker"
+                parallel_config.sd_worker_cls = \
+                    "vllm.worker.cpu_worker.CPUWorker"
+            else:
+                if envs.VLLM_USE_V1:
+                    parallel_config.worker_cls = \
+                        "vllm.v1.worker.cpu_worker.CPUWorker"
+                else:
+                    parallel_config.worker_cls = \
+                        "vllm.worker.cpu_worker.CPUWorker"
 
         # Note: workaround for v1 gpu_model_runner
         from vllm.config import CompilationLevel
         vllm_config.compilation_config.cudagraph_capture_sizes = []
 
         compilation_config = vllm_config.compilation_config
-        if vllm_config.compilation_config.level == CompilationLevel.PIECEWISE:
+        if (envs.VLLM_USE_V1 and vllm_config.compilation_config.level
+                == CompilationLevel.PIECEWISE):
 
             # Note: vLLM V1 is using PIECEWISE level compilation, which will
             # take time to compile kernels just-in-time with the inductor

vllm/platforms/tpu.py

@@ -6,6 +6,7 @@ from typing import TYPE_CHECKING, Optional, Union, cast
 import torch
 from tpu_info import device
 
+import vllm.envs as envs
 from vllm.inputs import ProcessorInputs, PromptType
 from vllm.logger import init_logger
 from vllm.sampling_params import SamplingParams, SamplingType
@@ -49,10 +50,12 @@ class TpuPlatform(Platform):
                 and selected_backend != _Backend.PALLAS_VLLM_V1):
             logger.info("Cannot use %s backend on TPU.", selected_backend)
 
-        if not use_v1:
+        if use_v1:
-            raise ValueError("TPU backend only supports V1.")
+            logger.info("Using Pallas V1 backend.")
-        logger.info("Using Pallas V1 backend.")
+            return "vllm.v1.attention.backends.pallas.PallasAttentionBackend"
-        return "vllm.v1.attention.backends.pallas.PallasAttentionBackend"
+        else:
+            logger.info("Using Pallas backend.")
+            return "vllm.attention.backends.pallas.PallasAttentionBackend"
 
     @classmethod
     def get_device_name(cls, device_id: int = 0) -> str:
@@ -65,7 +68,7 @@ class TpuPlatform(Platform):
 
     @classmethod
     def is_async_output_supported(cls, enforce_eager: Optional[bool]) -> bool:
-        return False
+        return not envs.VLLM_USE_V1
 
     @classmethod
     def get_punica_wrapper(cls) -> str:
@@ -114,19 +117,31 @@ class TpuPlatform(Platform):
                 "Using bfloat16 instead.", vllm_config.model_config.dtype)
             vllm_config.model_config.dtype = torch.bfloat16
 
-        from vllm.v1.attention.backends.pallas import PallasAttentionBackend
+        if envs.VLLM_USE_V1:
-        cache_config.block_size = PallasAttentionBackend.get_page_size(
+            from vllm.v1.attention.backends.pallas import (
-            vllm_config)  # type: ignore[assignment]
+                PallasAttentionBackend)
+            cache_config.block_size = PallasAttentionBackend.get_page_size(
+                vllm_config)  # type: ignore[assignment]
 
         parallel_config = vllm_config.parallel_config
         scheduler_config = vllm_config.scheduler_config
         if parallel_config.worker_cls == "auto":
             if scheduler_config.is_multi_step:
-                raise NotImplementedError(
+                if envs.VLLM_USE_V1:
-                    "Multi-step scheduling is not supported (and not "
+                    raise NotImplementedError(
-                    "needed) on vLLM V1. Please launch without "
+                        "Multi-step scheduling is not supported (and not "
-                    "--num-scheduler-steps.")
+                        "needed) on vLLM V1. Please launch without "
-            parallel_config.worker_cls = "vllm.v1.worker.tpu_worker.TPUWorker"
+                        "--num-scheduler-steps.")
+                else:
+                    parallel_config.worker_cls = \
+                        "vllm.worker.multi_step_tpu_worker.MultiStepTPUWorker"
+            else:
+                if envs.VLLM_USE_V1:
+                    parallel_config.worker_cls = \
+                        "vllm.v1.worker.tpu_worker.TPUWorker"
+                else:
+                    parallel_config.worker_cls = \
+                        "vllm.worker.tpu_worker.TPUWorker"
 
         assert not vllm_config.speculative_config, (
             "Speculative decoding is not yet supported for TPU backend")
@@ -174,9 +189,13 @@ class TpuPlatform(Platform):
         processed_inputs: ProcessorInputs,
     ) -> None:
         """Raises if this request is unsupported on this platform"""
-        if (isinstance(params, SamplingParams)
+        if isinstance(params, SamplingParams):
-                and params.sampling_type == SamplingType.RANDOM_SEED):
+            if params.guided_decoding is not None and not envs.VLLM_USE_V1:
-            raise ValueError("Torch XLA does not support per-request seed.")
+                raise ValueError("Structured output is not supported on "
+                                 f"{cls.device_name} V0.")
+            if params.sampling_type == SamplingType.RANDOM_SEED:
+                raise ValueError(
+                    "Torch XLA does not support per-request seed.")
 
 
 try:

vllm/platforms/xpu.py

@@ -39,10 +39,12 @@ class XPUPlatform(Platform):
         if selected_backend != _Backend.IPEX:
             logger.info("Cannot use %s backend on XPU.", selected_backend)
         use_v1 = envs.VLLM_USE_V1
-        if not use_v1:
+        if use_v1:
-            raise ValueError("XPU backend only supports V1.")
+            logger.info("Using Flash Attention backend on V1 engine.")
-        logger.info("Using Flash Attention backend on V1 engine.")
+            return "vllm.v1.attention.backends.flash_attn.FlashAttentionBackend"
-        return "vllm.v1.attention.backends.flash_attn.FlashAttentionBackend"
+        else:
+            logger.info("Using IPEX attention backend.")
+            return "vllm.attention.backends.ipex_attn.IpexAttnBackend"
 
     @classmethod
     def get_device_capability(
@@ -75,7 +77,10 @@ class XPUPlatform(Platform):
         cache_config = vllm_config.cache_config
         # in V1(or with ipex chunked prefill) block_size is 64
         if cache_config and cache_config.block_size is None:
-            cache_config.block_size = 64
+            if envs.VLLM_USE_V1:
+                cache_config.block_size = 64
+            else:
+                cache_config.block_size = 16
 
         # Instances created using VllmConfig() typically have model_config as
         # None by default. The modification involves adding a check to prevent
@@ -101,7 +106,11 @@ class XPUPlatform(Platform):
 
         # check and update parallel config
         parallel_config = vllm_config.parallel_config
-        parallel_config.worker_cls = "vllm.v1.worker.xpu_worker.XPUWorker"
+        if envs.VLLM_USE_V1:
+            parallel_config.worker_cls =\
+                "vllm.v1.worker.xpu_worker.XPUWorker"
+        else:
+            parallel_config.worker_cls = "vllm.worker.xpu_worker.XPUWorker"
 
         if parallel_config.distributed_executor_backend is None:
             if parallel_config.world_size > 1:

vllm/worker/cpu_enc_dec_model_runner.py

@@ -0,0 +1,326 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import dataclasses
+from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple, Type, cast
+
+import torch
+
+from vllm.attention import AttentionMetadata
+from vllm.forward_context import set_forward_context
+from vllm.model_executor import SamplingMetadata
+from vllm.model_executor.layers.sampler import SamplerOutput
+from vllm.multimodal import MultiModalKwargs
+from vllm.sequence import IntermediateTensors, SequenceGroupMetadata
+from vllm.utils import make_tensor_with_pad
+from vllm.worker.cpu_model_runner import (CPUModelRunnerBase,
+                                          ModelInputForCPUBuilder,
+                                          ModelInputForCPUWithSamplingMetadata)
+from vllm.worker.model_runner_base import (
+    _add_attn_metadata_broadcastable_dict,
+    _add_sampling_metadata_broadcastable_dict)
+
+if TYPE_CHECKING:
+    from vllm.attention.backends.abstract import AttentionBackend
+
+
+@dataclasses.dataclass(frozen=True)
+class EncoderDecoderModelInputForCPU(ModelInputForCPUWithSamplingMetadata):
+    """
+    Used by the EncoderDecoderModelRunner.
+    """
+    encoder_input_tokens: Optional[torch.Tensor] = None
+    encoder_input_positions: Optional[torch.Tensor] = None
+
+    def as_broadcastable_tensor_dict(self) -> Dict[str, Any]:
+        tensor_dict = {
+            "input_tokens": self.input_tokens,
+            "input_positions": self.input_positions,
+            "encoder_input_tokens": self.encoder_input_tokens,
+            "encoder_input_positions": self.encoder_input_positions,
+            "multi_modal_kwargs": self.multi_modal_kwargs,
+        }
+        _add_attn_metadata_broadcastable_dict(tensor_dict, self.attn_metadata)
+        _add_sampling_metadata_broadcastable_dict(tensor_dict,
+                                                  self.sampling_metadata)
+        return tensor_dict
+
+    @classmethod
+    def from_broadcasted_tensor_dict(
+        cls,
+        tensor_dict: Dict[str, Any],
+        attn_backend: Optional["AttentionBackend"] = None,
+    ) -> "EncoderDecoderModelInputForCPU":
+        return cast(
+            EncoderDecoderModelInputForCPU,
+            super().from_broadcasted_tensor_dict(tensor_dict, attn_backend))
+
+
+class CPUEncoderDecoderModelRunner(
+        CPUModelRunnerBase[EncoderDecoderModelInputForCPU]):
+    _model_input_cls: Type[EncoderDecoderModelInputForCPU] = (
+        EncoderDecoderModelInputForCPU)
+    _builder_cls: Type[ModelInputForCPUBuilder] = ModelInputForCPUBuilder
+
+    def _list_to_int32_tensor(
+        self,
+        _list: List[int],
+    ) -> torch.Tensor:
+        return torch.tensor(_list, dtype=torch.int32, device=self.device)
+
+    def _list_to_long_tensor(
+        self,
+        _list: List[int],
+    ) -> torch.Tensor:
+        return torch.tensor(_list, dtype=torch.long, device=self.device)
+
+    def _empty_int32_tensor(self) -> torch.Tensor:
+        return self._list_to_int32_tensor([])
+
+    def _empty_long_tensor(self) -> torch.Tensor:
+        return self._list_to_long_tensor([])
+
+    def make_model_input_from_broadcasted_tensor_dict(
+            self, tensor_dict: Dict[str,
+                                    Any]) -> EncoderDecoderModelInputForCPU:
+        return EncoderDecoderModelInputForCPU.from_broadcasted_tensor_dict(
+            tensor_dict,
+            attn_backend=self.attn_backend,
+        )
+
+    def prepare_model_input(
+        self,
+        seq_group_metadata_list: List[SequenceGroupMetadata],
+        virtual_engine: int = 0,
+        finished_requests_ids: Optional[List[str]] = None
+    ) -> EncoderDecoderModelInputForCPU:
+        model_input = self._prepare_model_input_tensors(
+            seq_group_metadata_list, finished_requests_ids)
+        (
+            attn_metadata,
+            encoder_input_tokens_tensor,
+            encoder_input_positions_tensor,
+        ) = self._prepare_encoder_model_input_tensors(seq_group_metadata_list,
+                                                      model_input)
+        # Sampling metadata is only required for the final pp group
+        generators = self.get_generators(finished_requests_ids)
+        sampling_metadata = SamplingMetadata.prepare(seq_group_metadata_list,
+                                                     model_input.seq_lens,
+                                                     model_input.query_lens,
+                                                     self.device,
+                                                     pin_memory=False,
+                                                     generators=generators)
+        return dataclasses.replace(
+            model_input,
+            sampling_metadata=sampling_metadata,
+            attn_metadata=attn_metadata,
+            encoder_input_tokens=encoder_input_tokens_tensor,
+            encoder_input_positions=encoder_input_positions_tensor,
+            virtual_engine=virtual_engine,
+        )
+
+    def _prepare_encoder_model_input_tensors(
+        self,
+        seq_group_metadata_list: List[SequenceGroupMetadata],
+        model_input: EncoderDecoderModelInputForCPU,
+    ) -> Tuple[AttentionMetadata, Optional[torch.Tensor],
+               Optional[torch.Tensor]]:
+        """Helper method to prepare the encoder- and cross-attn-related
+        model inputs based on a given sequence group. These additional inputs
+        are used to augment an already-computed `EncoderDecoderModelInput`
+        data structure which already has decoder-related model inputs
+        populated.
+
+        Sets the following attn_metadata fields:
+        * `num_encoder_tokens`
+        * `encoder_seq_lens`
+        * `encoder_seq_lens_tensor`
+        * `max_encoder_seq_len`
+        * `cross_slot_mapping`
+        * `cross_block_tables`
+
+        Constructs a new model inputs data structure, based on
+        (1) the existing fields in the `model_inputs` argument,
+        and (2) the following additional fields which are
+        computed (or in the case of `attn_metadata`, updated) 
+        by this function:
+        * attn_metadata
+        * encoder_input_tokens
+        * encoder_input_positions
+
+        Arguments:
+
+        * seq_group_metadata_list: list of sequence groups for which to
+                                   compute inputs
+        * model_inputs: model inputs data structure with decoder-oriented
+                        fields already computed.
+
+        Return:
+
+        * Updated model inputs data structure
+        """
+
+        if len(seq_group_metadata_list) == 0:
+            return (model_input.attn_metadata, None, None)
+
+        # Since we are not supporting chunked prefill either the entire
+        # batch is prefill or it is decode
+        is_prompt = seq_group_metadata_list[0].is_prompt
+
+        # Build encoder inputs
+        encoder_seq_lens: List[int] = []
+        if is_prompt:
+            # Prefill phase.
+            cross_block_tables = self._empty_int32_tensor().view(
+                len(seq_group_metadata_list), -1)
+
+            # Extract input tokens/positions, cross-attention slot-mapping,
+            # & seq len from each sequence group metadata
+            (
+                encoder_input_tokens,
+                encoder_input_positions,
+                cross_slot_mapping,
+            ) = (
+                [],
+                [],
+                [],
+            )
+            for seq_group_metadata in seq_group_metadata_list:
+                # Build seq lens
+                seq_len = seq_group_metadata.encoder_seq_data.get_len()
+                token_ids = seq_group_metadata.encoder_seq_data.get_token_ids()
+                encoder_seq_lens.append(seq_len)
+
+                # Build slot mapping
+                for i in range(0, seq_len):
+                    block_number = seq_group_metadata.cross_block_table[
+                        i // self.block_size]
+                    block_offset = i % self.block_size
+                    slot = block_number * self.block_size + block_offset
+                    cross_slot_mapping.append(slot)
+
+                # Build encoder input tokens
+                encoder_input_tokens.extend(token_ids)
+                encoder_input_positions.extend(list(range(0, seq_len)))
+
+            # Convert tokens/positions & cross-attention
+            # slot-mapping to encoder input tensors
+            encoder_input_tokens_tensor = self._list_to_long_tensor(
+                encoder_input_tokens)
+            encoder_input_positions_tensor = self._list_to_long_tensor(
+                encoder_input_positions)
+            cross_slot_mapping_tensor = self._list_to_long_tensor(
+                cross_slot_mapping)
+
+        else:
+            # Decode phase.
+            encoder_input_tokens_tensor = self._empty_long_tensor()
+            encoder_input_positions_tensor = self._empty_long_tensor()
+            cross_slot_mapping_tensor = self._empty_long_tensor()
+            # Extract cross-attention block tables &
+            # seq len from each sequence group metadata.
+            # Cross-attention block tables are empty
+            # during vLLM memory profiling.
+            cross_block_tables = []
+            for seq_group_metadata in seq_group_metadata_list:
+                for _ in range(len(seq_group_metadata.seq_data)):
+                    encoder_seq_lens.append(
+                        seq_group_metadata.encoder_seq_data.get_len())
+                    cross_block_table = seq_group_metadata.cross_block_table
+                    cross_block_tables.append([] if (
+                        cross_block_table is None) else cross_block_table)
+
+            max_len_of_block_table = max(
+                len(block_table) for block_table in cross_block_tables)
+
+            cross_block_tables = make_tensor_with_pad(
+                cross_block_tables,
+                max_len=max_len_of_block_table,
+                pad=0,
+                dtype=torch.int32,
+                device=self.device,
+            )
+
+        # Compute encoder sequence lengths & encoder
+        # sequence starting offset tensors
+        max_encoder_seq_len = max(encoder_seq_lens, default=0)
+        encoder_seq_lens_tensor = self._list_to_int32_tensor(encoder_seq_lens)
+        encoder_seq_start_loc = torch.zeros(encoder_seq_lens_tensor.shape[0] +
+                                            1,
+                                            dtype=torch.int32,
+                                            device=self.device)
+        torch.cumsum(encoder_seq_lens_tensor,
+                     dim=0,
+                     dtype=encoder_seq_start_loc.dtype,
+                     out=encoder_seq_start_loc[1:])
+
+        # Update attention metadata with encoder-oriented attributes
+        attn_metadata = model_input.attn_metadata
+        assert attn_metadata is not None
+        (
+            attn_metadata.num_encoder_tokens,
+            attn_metadata.encoder_seq_lens,
+            attn_metadata.encoder_seq_lens_tensor,
+            attn_metadata.max_encoder_seq_len,
+            attn_metadata.cross_slot_mapping,
+            attn_metadata.cross_block_tables,
+        ) = (
+            sum(encoder_seq_lens),
+            encoder_seq_lens,
+            encoder_seq_lens_tensor,
+            max_encoder_seq_len,
+            cross_slot_mapping_tensor,
+            cross_block_tables,
+        )
+
+        return (attn_metadata, encoder_input_tokens_tensor,
+                encoder_input_positions_tensor)
+
+    @torch.no_grad()
+    def execute_model(
+        self,
+        model_input: EncoderDecoderModelInputForCPU,
+        kv_caches: List[torch.Tensor],
+        intermediate_tensors: Optional[IntermediateTensors] = None,
+        num_steps: int = 1,
+    ) -> Optional[List[SamplerOutput]]:
+        if num_steps > 1:
+            raise ValueError(
+                "CPU worker does not support multi-step execution.")
+
+        model_executable = self.model
+        execute_model_kwargs = {
+            "input_ids":
+            model_input.input_tokens,
+            "positions":
+            model_input.input_positions,
+            "encoder_input_ids":
+            model_input.encoder_input_tokens,
+            "encoder_positions":
+            model_input.encoder_input_positions,
+            **MultiModalKwargs.as_kwargs(
+                model_input.multi_modal_kwargs or {},
+                device=self.device,
+            ),
+            "intermediate_tensors":
+            intermediate_tensors,
+        }
+
+        with set_forward_context(model_input.attn_metadata, self.vllm_config,
+                                 model_input.virtual_engine):
+            hidden_states = model_executable(**execute_model_kwargs)
+
+        # Compute the logits.
+        logits = self.model.compute_logits(hidden_states,
+                                           model_input.sampling_metadata)
+
+        # Only perform sampling in the driver worker.
+        if not self.is_driver_worker:
+            return []
+
+        # Sample the next token.
+        output = self.sampler(
+            logits=logits,
+            sampling_metadata=model_input.sampling_metadata,
+        )
+        return [output]

vllm/worker/cpu_model_runner.py

@@ -0,0 +1,671 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import dataclasses
+import weakref
+from collections import defaultdict
+from dataclasses import dataclass
+from typing import (TYPE_CHECKING, Any, Dict, List, Optional, Set, Type,
+                    TypeVar, Union)
+
+import torch
+from torch import nn
+
+from vllm.attention import AttentionMetadata, get_attn_backend
+from vllm.config import VllmConfig
+from vllm.forward_context import set_forward_context
+from vllm.logger import init_logger
+from vllm.lora.layers import LoRAMapping
+from vllm.lora.request import LoRARequest
+from vllm.lora.worker_manager import LRUCacheWorkerLoRAManager
+from vllm.model_executor import SamplingMetadata
+from vllm.model_executor.layers.rotary_embedding import MRotaryEmbedding
+from vllm.model_executor.layers.sampler import SamplerOutput, get_sampler
+from vllm.model_executor.model_loader import get_model
+from vllm.model_executor.models import supports_lora, supports_multimodal
+from vllm.multimodal import (BatchedTensorInputs, MultiModalKwargs,
+                             MultiModalPlaceholderMap)
+from vllm.sequence import (IntermediateTensors, SequenceData,
+                           SequenceGroupMetadata)
+from vllm.worker.model_runner_base import (
+    ModelRunnerBase, ModelRunnerInputBase, ModelRunnerInputBuilderBase,
+    _add_attn_metadata_broadcastable_dict,
+    _add_sampling_metadata_broadcastable_dict,
+    _init_attn_metadata_from_tensor_dict,
+    _init_sampling_metadata_from_tensor_dict)
+
+if TYPE_CHECKING:
+    from vllm.attention.backends.abstract import AttentionBackend
+
+logger = init_logger(__name__)
+
+TModelInputForCPU = TypeVar('TModelInputForCPU', bound="ModelInputForCPU")
+_PAD_SLOT_ID = -1
+
+
+@dataclass(frozen=True)
+class ModelInputForCPU(ModelRunnerInputBase):
+    """
+    Base class contains metadata needed for the base model forward pass on CPU
+    """
+    input_tokens: Optional[torch.Tensor] = None
+    input_positions: Optional[torch.Tensor] = None
+    token_type_ids: Optional[torch.Tensor] = None
+    attn_metadata: Optional["AttentionMetadata"] = None
+    multi_modal_kwargs: Optional[BatchedTensorInputs] = None
+    virtual_engine: Optional[int] = None
+    seq_lens: Optional[List[int]] = None
+    query_lens: Optional[List[int]] = None
+    lora_mapping: Optional["LoRAMapping"] = None
+    lora_requests: Optional[Set[LoRARequest]] = None
+
+    def as_broadcastable_tensor_dict(
+            self) -> Dict[str, Union[int, torch.Tensor]]:
+        tensor_dict = {
+            "input_tokens": self.input_tokens,
+            "input_positions": self.input_positions,
+            "token_type_ids": self.token_type_ids,
+            "multi_modal_kwargs": self.multi_modal_kwargs,
+            "lora_requests": self.lora_requests,
+            "lora_mapping": self.lora_mapping,
+        }
+        _add_attn_metadata_broadcastable_dict(tensor_dict, self.attn_metadata)
+
+        return tensor_dict
+
+    @classmethod
+    def from_broadcasted_tensor_dict(
+        cls: Type[TModelInputForCPU],
+        tensor_dict: Dict[str, Any],
+        attn_backend: Optional["AttentionBackend"] = None
+    ) -> TModelInputForCPU:
+        if attn_backend is not None:
+            tensor_dict = _init_attn_metadata_from_tensor_dict(
+                attn_backend, tensor_dict)
+        return cls(**tensor_dict)
+
+
+@dataclass(frozen=True)
+class ModelInputForCPUWithSamplingMetadata(ModelInputForCPU):
+    """
+    Used by the ModelRunner.
+    """
+    sampling_metadata: Optional["SamplingMetadata"] = None
+    is_prompt: Optional[bool] = None
+
+    def as_broadcastable_tensor_dict(self) -> Dict[str, Any]:
+        tensor_dict = {
+            "input_tokens": self.input_tokens,
+            "input_positions": self.input_positions,
+            "token_type_ids": self.token_type_ids,
+            "multi_modal_kwargs": self.multi_modal_kwargs,
+        }
+        _add_attn_metadata_broadcastable_dict(tensor_dict, self.attn_metadata)
+        _add_sampling_metadata_broadcastable_dict(tensor_dict,
+                                                  self.sampling_metadata)
+        return tensor_dict
+
+    @classmethod
+    def from_broadcasted_tensor_dict(
+        cls,
+        tensor_dict: Dict[str, Any],
+        attn_backend: Optional["AttentionBackend"] = None,
+    ) -> "ModelInputForCPUWithSamplingMetadata":
+        tensor_dict = _init_sampling_metadata_from_tensor_dict(tensor_dict)
+        if attn_backend is not None:
+            tensor_dict = _init_attn_metadata_from_tensor_dict(
+                attn_backend, tensor_dict)
+        return cls(**tensor_dict)
+
+
+class ModelInputForCPUBuilder(ModelRunnerInputBuilderBase[ModelInputForCPU]):
+
+    class ModelInputData:
+
+        def __init__(self, use_mrope: bool):
+            self.use_mrope = use_mrope
+            self.input_tokens: List[int] = []
+            self.input_positions: List[int] = []
+            self.token_type_ids: Optional[List[int]] = []
+            self.seq_lens: List[int] = []
+            self.query_lens: List[int] = []
+            self.prefill_block_tables: List[List[int]] = []
+            self.decode_block_tables: List[List[int]] = []
+            self.max_decode_seq_len: int = 0
+            self.num_prefills: int = 0
+            self.num_prefill_tokens: int = 0
+            self.num_decode_tokens: int = 0
+            self.slot_mapping: List[int] = []
+            self.multi_modal_inputs_list: List[MultiModalKwargs] = []
+            self.multi_modal_placeholder_maps: Dict[
+                str, MultiModalPlaceholderMap] = defaultdict(
+                    MultiModalPlaceholderMap)
+            self.input_mrope_positions: List[List[int]] = [[]
+                                                           for _ in range(3)]
+
+    def __init__(self,
+                 runner: "CPUModelRunner",
+                 finished_requests_ids: Optional[List[str]] = None) -> None:
+        super().__init__()
+        self.runner = runner
+        self.chunked_prefill = (runner.scheduler_config.chunked_prefill_enabled
+                                or runner.cache_config.enable_prefix_caching)
+        self.model_input_cls = self.runner._model_input_cls
+        self.attn_backend = self.runner.attn_backend
+        self.sliding_window = self.runner.sliding_window
+        self.block_size = self.runner.block_size
+        self.device = self.runner.device
+        self.enable_lora = self.runner.lora_config is not None
+        if self.runner.attn_backend is not None:
+            # spec decode (e.g. Medusa) does not have atten backend
+            attn_backend = self.runner.attn_backend
+            self.att_metadata_builder = attn_backend.get_builder_cls()(self)
+
+    def prepare(self,
+                finished_requests_ids: Optional[List[str]] = None) -> None:
+        self.seq_group_metadata_list: List[SequenceGroupMetadata] = []
+        self.input_data = ModelInputForCPUBuilder.ModelInputData(
+            self.runner.model_config.uses_mrope)
+        self.att_metadata_builder.prepare()
+
+    def add_seq_group(self, seq_group_metadata: SequenceGroupMetadata):
+        self.seq_group_metadata_list.append(seq_group_metadata)
+
+    def set_seq_group_list(
+            self, seq_group_metadata_list: List[SequenceGroupMetadata]):
+        self.seq_group_metadata_list = seq_group_metadata_list
+
+    def build(self) -> ModelInputForCPU:
+        self._build_input_data()
+
+        input_data = self.input_data
+        input_tokens = torch.tensor(input_data.input_tokens,
+                                    dtype=torch.long,
+                                    device="cpu")
+        input_positions = torch.tensor(
+            input_data.input_positions
+            if not any(input_data.input_mrope_positions) else
+            input_data.input_mrope_positions,
+            dtype=torch.long,
+            device="cpu")
+        token_type_ids = torch.tensor(input_data.token_type_ids,
+                                    dtype=torch.long,
+                                    device="cpu") \
+                                    if input_data.token_type_ids else None
+
+        # For multi-modal models
+        multi_modal_kwargs = None
+        if len(input_data.multi_modal_inputs_list) != 0:
+            multi_modal_kwargs = MultiModalKwargs.batch(
+                input_data.multi_modal_inputs_list)
+
+        attn_metadata = self.att_metadata_builder.build(
+            input_data.seq_lens, input_data.query_lens, -1, -1)
+
+        is_prompt = (self.seq_group_metadata_list[0].is_prompt
+                     if self.seq_group_metadata_list else None)
+        # LoRA data.
+        lora_requests = set()
+        lora_mapping = None
+        if self.enable_lora:
+            lora_requests = set(seq.lora_request
+                                for seq in self.seq_group_metadata_list
+                                if seq.lora_request is not None)
+
+            lora_mapping = self._prepare_lora_input(
+                self.seq_group_metadata_list, is_prompt)
+
+        return self.model_input_cls(input_tokens=input_tokens,
+                                    input_positions=input_positions,
+                                    token_type_ids=token_type_ids,
+                                    seq_lens=input_data.seq_lens,
+                                    query_lens=input_data.query_lens,
+                                    attn_metadata=attn_metadata,
+                                    multi_modal_kwargs=multi_modal_kwargs,
+                                    lora_mapping=lora_mapping,
+                                    lora_requests=lora_requests)
+
+    def _build_input_data(self):
+        for seq_group_metadata in self.seq_group_metadata_list:
+            for seq_id, seq_data in seq_group_metadata.seq_data.items():
+                if seq_group_metadata.is_prompt:
+                    self._compute_prompt_input_tokens(self.input_data,
+                                                      seq_group_metadata,
+                                                      seq_data, seq_id)
+                    if seq_group_metadata.multi_modal_data:
+                        self._compute_multi_modal_input(
+                            seq_group_metadata, seq_data)
+                else:
+                    self._compute_decode_input_tokens(self.input_data,
+                                                      seq_group_metadata,
+                                                      seq_data, seq_id)
+
+    def _compute_decode_input_tokens(self, data: ModelInputData,
+                                     seq_group_metadata: SequenceGroupMetadata,
+                                     seq_data: SequenceData, seq_id: int):
+        """
+        Compute decode input tokens, positions, block table and slot mapping.
+        """
+        block_size = self.runner.block_size
+
+        block_table = seq_group_metadata.block_tables[seq_id]
+        seq_len = seq_data.get_len()
+        context_len = seq_data.get_num_computed_tokens()
+
+        tokens = seq_data.get_last_token_id()
+        token_positions = seq_len - 1
+        block_number = block_table[token_positions // block_size]
+        block_offset = token_positions % block_size
+        slot = block_number * block_size + block_offset
+
+        # For paged_attention kernel
+        if self.runner.sliding_window:
+            start_idx = max(0, seq_len - self.runner.sliding_window)
+            start_block = start_idx // block_size
+            start_idx = start_block * block_size
+            seq_len = seq_len - start_idx
+            block_table = block_table[start_block:]
+
+        # For MRotaryEmbedding
+        if seq_data.mrope_position_delta is not None:
+            next_pos = MRotaryEmbedding.get_next_input_positions(
+                seq_data.mrope_position_delta,
+                context_len,
+                seq_len,
+            )
+            for idx in range(3):
+                data.input_mrope_positions[idx].extend(  # type: ignore
+                    next_pos[idx])
+        else:
+            data.input_positions.append(token_positions)  # type: ignore
+
+        # Update fields
+        data.input_tokens.append(tokens)
+        data.max_decode_seq_len = max(data.max_decode_seq_len, seq_len)
+        data.num_decode_tokens += 1
+        data.slot_mapping.append(slot)
+        data.decode_block_tables.append(block_table)
+        data.query_lens.append(1)
+        data.seq_lens.append(seq_len)
+
+    def _compute_prompt_input_tokens(self, data: ModelInputData,
+                                     seq_group_metadata: SequenceGroupMetadata,
+                                     seq_data: SequenceData, seq_id: int):
+        """
+        Compute prompt input tokens, positions, block table and slot mapping.
+        """
+        token_chunk_size = seq_group_metadata.token_chunk_size
+        block_size = self.runner.block_size
+
+        block_table = seq_group_metadata.block_tables[seq_id]
+        seq_len = seq_data.get_len()
+        context_len = seq_data.get_num_computed_tokens()
+        seq_len = min(seq_len, context_len + token_chunk_size)
+
+        # For prefix caching
+        prefix_cache_block_num = len(seq_group_metadata.computed_block_nums)
+        if prefix_cache_block_num > 0:
+            prefix_cache_len = (prefix_cache_block_num *
+                                self.runner.block_size)
+            if prefix_cache_len <= context_len:
+                # We already passed the cache hit region,
+                # so do normal computation.
+                pass
+            elif context_len < prefix_cache_len < seq_len:
+                # Partial hit. Compute the missing part.
+                context_len = prefix_cache_len
+                token_chunk_size = seq_len - context_len
+            elif seq_len <= prefix_cache_len:
+                # Full hit. Only compute the last token to avoid
+                # erroneous behavior. FIXME: Ideally we should directly
+                # mark all tokens as computed in the scheduler and do not
+                # schedule this sequence, so this case should not happen.
+                context_len = seq_len - 1
+                token_chunk_size = 1
+
+        tokens = seq_data.get_token_ids()
+        tokens = tokens[context_len:seq_len]
+        token_positions = range(context_len, seq_len)
+        token_types = seq_group_metadata.token_type_ids
+
+        # For encoder-only models, the block_table is None,
+        # and there is no need to initialize the slot_mapping.
+        if block_table is not None:
+            slot_mapping = [_PAD_SLOT_ID] * len(token_positions)
+            for i, pos in enumerate(token_positions):
+                block_number = block_table[pos // block_size]
+                block_offset = pos % block_size
+                slot = block_number * block_size + block_offset
+                slot_mapping[i] = slot
+            data.slot_mapping.extend(slot_mapping)
+
+        # The MROPE positions are prepared in _compute_multi_modal_input
+        data.input_positions.extend(token_positions)
+
+        if data.token_type_ids is not None:
+            data.token_type_ids.extend(token_types if token_types else [])
+
+        # Update fields
+        data.input_tokens.extend(tokens)
+        data.num_prefills += 1
+        data.num_prefill_tokens += len(tokens)
+        data.query_lens.append(len(tokens))
+        data.prefill_block_tables.append(block_table)
+        data.seq_lens.append(seq_len)
+
+    def _compute_multi_modal_input(self,
+                                   seq_group_metadata: SequenceGroupMetadata,
+                                   seq_data: SequenceData):
+        computed_len = seq_data.get_num_computed_tokens()
+        seq_len = self.input_data.seq_lens[-1]
+
+        # NOTE: mm_kwargs only includes the subset of multi-modal items that
+        # intersect with the current prefill positions.
+        mm_kwargs, placeholder_maps = MultiModalPlaceholderMap.from_seq_group(
+            seq_group_metadata, range(computed_len, seq_len))
+
+        if not mm_kwargs:
+            return
+
+        # special processing for mrope position deltas.
+        if self.runner.model_config.uses_mrope:
+            assert not self.chunked_prefill, \
+                "MROPE on CPU does not support chunked-prefill."
+
+            image_grid_thw = mm_kwargs.get("image_grid_thw", None)
+            video_grid_thw = mm_kwargs.get("video_grid_thw", None)
+            audio_feature_lengths = mm_kwargs.get("audio_feature_lengths",
+                                                  None)
+            assert (
+                image_grid_thw is not None or video_grid_thw is not None
+                or audio_feature_lengths is not None), (
+                    "mrope embedding type requires multi-modal input mapper "
+                    "returns 'image_grid_thw' or 'video_grid_thw' or "
+                    "'audio_feature_lengths'.")
+
+            second_per_grid_ts = mm_kwargs.get("second_per_grid_ts", None)
+            use_audio_in_video = mm_kwargs.get("use_audio_in_video", False)
+            hf_config = self.runner.model_config.hf_config
+            token_ids = seq_data.get_token_ids()
+
+            mrope_positions, mrope_position_delta = \
+                MRotaryEmbedding.get_input_positions(
+                    token_ids,
+                    hf_config=hf_config,
+                    image_grid_thw=image_grid_thw,
+                    video_grid_thw=video_grid_thw,
+                    second_per_grid_ts=second_per_grid_ts,
+                    context_len=computed_len,
+                    audio_feature_lengths=audio_feature_lengths,
+                    use_audio_in_video=use_audio_in_video,
+                )
+            seq_data.mrope_position_delta = mrope_position_delta
+
+            for i in range(3):
+                self.input_data.input_mrope_positions[  # type: ignore
+                    i].extend(mrope_positions[i])
+
+        self.input_data.multi_modal_inputs_list.append(mm_kwargs)
+        for modality, placeholder_map in placeholder_maps.items():
+            self.input_data.multi_modal_placeholder_maps[modality].extend(
+                placeholder_map)
+
+    def _prepare_lora_input(
+            self, seq_group_metadata_list: List[SequenceGroupMetadata],
+            is_prefill: bool) -> LoRAMapping:
+        index_mapping = []
+        prompt_mapping = []
+        for seq in seq_group_metadata_list:
+            lora_id = seq.lora_int_id
+            query_len = seq.token_chunk_size
+
+            index_mapping += [lora_id] * query_len
+            prompt_mapping += [lora_id] * (
+                query_len if seq.sampling_params
+                and seq.sampling_params.prompt_logprobs is not None else 1)
+
+        return LoRAMapping(index_mapping=tuple(index_mapping),
+                           prompt_mapping=tuple(prompt_mapping),
+                           is_prefill=is_prefill)
+
+
+class CPUModelRunnerBase(ModelRunnerBase[TModelInputForCPU]):
+    """
+    Helper class for shared methods between CPU model runners.
+    """
+    _model_input_cls: Type[TModelInputForCPU]
+    _builder_cls: Type[ModelInputForCPUBuilder]
+    builder: ModelInputForCPUBuilder
+
+    def __init__(
+        self,
+        vllm_config: VllmConfig,
+        kv_cache_dtype: Optional[str] = "auto",
+        is_driver_worker: bool = False,
+        return_hidden_states: bool = False,
+        *args,
+        **kwargs,
+    ):
+        ModelRunnerBase.__init__(self, vllm_config)
+        model_config = self.model_config
+        cache_config = self.cache_config
+
+        self.is_driver_worker = is_driver_worker
+        self.return_hidden_states = return_hidden_states
+
+        self.device = self.device_config.device
+        self.pin_memory = False
+
+        self.kv_cache_dtype = kv_cache_dtype
+        self.sliding_window = model_config.get_sliding_window()
+        self.block_size = cache_config.block_size
+        num_attn_heads = self.model_config.get_num_attention_heads(
+            self.parallel_config)
+        needs_attn_backend = (num_attn_heads != 0
+                              or self.model_config.is_attention_free)
+        self.attn_backend = get_attn_backend(
+            self.model_config.get_head_size(),
+            self.model_config.dtype,
+            self.kv_cache_dtype,
+            self.block_size,
+            self.model_config.is_attention_free,
+            use_mla=self.model_config.use_mla,
+        ) if needs_attn_backend else None
+
+        # Lazy initialization.
+        self.model: nn.Module  # Set after init_Model
+        # Set after load_model.
+        self.lora_manager: Optional[LRUCacheWorkerLoRAManager] = None
+        self.sampler = get_sampler()
+
+        if hasattr(self, "_builder_cls"):
+            # multi-step model runner does not have `_builder_cls`
+            self.builder = self._builder_cls(weakref.proxy(self))
+
+    def load_model(self) -> None:
+        self.model = get_model(vllm_config=self.vllm_config)
+
+        if self.lora_config:
+            assert supports_lora(
+                self.model
+            ), f"{self.model.__class__.__name__} does not support LoRA yet."
+
+            if supports_multimodal(self.model):
+                logger.warning("Regarding multimodal models, vLLM currently "
+                               "only supports adding LoRA to language model.")
+
+            # Use get_text_config() in case of multimodal models
+            text_config = self.model_config.hf_config.get_text_config()
+
+            self.lora_manager = LRUCacheWorkerLoRAManager(
+                self.scheduler_config.max_num_seqs,
+                self.scheduler_config.max_num_batched_tokens,
+                self.vocab_size,
+                self.lora_config,
+                self.device,
+                self.model.embedding_modules,
+                self.model.embedding_padding_modules,
+                max_position_embeddings=text_config.max_position_embeddings,
+            )
+            self.model = self.lora_manager.create_lora_manager(self.model)
+
+    def get_model(self) -> nn.Module:
+        return self.model
+
+    def _prepare_model_input_tensors(
+        self,
+        seq_group_metadata_list: List[SequenceGroupMetadata],
+        finished_requests_ids: Optional[List[str]] = None
+    ) -> TModelInputForCPU:
+        """Helper method to prepare the model input based on a given sequence
+        group. Prepares metadata needed for the base model forward pass but not
+        metadata for possible additional steps, e.g., sampling.
+
+        """
+        self.builder.prepare(finished_requests_ids)
+        self.builder.set_seq_group_list(seq_group_metadata_list)
+
+        return self.builder.build()  # type: ignore
+
+    @property
+    def vocab_size(self) -> int:
+        return self.model_config.get_vocab_size()
+
+    def remove_all_loras(self):
+        if not self.lora_manager:
+            raise RuntimeError("LoRA is not enabled.")
+        self.lora_manager.remove_all_adapters()
+
+    def set_active_loras(self, lora_requests: Set[LoRARequest],
+                         lora_mapping: LoRAMapping) -> None:
+        if not self.lora_manager:
+            raise RuntimeError("LoRA is not enabled.")
+        self.lora_manager.set_active_adapters(lora_requests, lora_mapping)
+
+    def add_lora(self, lora_request: LoRARequest) -> bool:
+        if not self.lora_manager:
+            raise RuntimeError("LoRA is not enabled.")
+        return self.lora_manager.add_adapter(lora_request)
+
+    def remove_lora(self, lora_id: int) -> bool:
+        if not self.lora_manager:
+            raise RuntimeError("LoRA is not enabled.")
+        return self.lora_manager.remove_adapter(lora_id)
+
+    def pin_lora(self, lora_id: int) -> bool:
+        if not self.lora_manager:
+            raise RuntimeError("LoRA is not enabled.")
+        return self.lora_manager.pin_adapter(lora_id)
+
+    def list_loras(self) -> Set[int]:
+        if not self.lora_manager:
+            raise RuntimeError("LoRA is not enabled.")
+        return self.lora_manager.list_adapters()
+
+
+class CPUModelRunner(CPUModelRunnerBase[ModelInputForCPUWithSamplingMetadata]):
+    _model_input_cls: Type[ModelInputForCPUWithSamplingMetadata] = (
+        ModelInputForCPUWithSamplingMetadata)
+    _builder_cls: Type[ModelInputForCPUBuilder] = ModelInputForCPUBuilder
+
+    def make_model_input_from_broadcasted_tensor_dict(
+        self,
+        tensor_dict: Dict[str, Any],
+    ) -> ModelInputForCPUWithSamplingMetadata:
+        return ModelInputForCPUWithSamplingMetadata.from_broadcasted_tensor_dict(  # noqa: E501
+            tensor_dict,
+            attn_backend=self.attn_backend,
+        )
+
+    def prepare_model_input(
+        self,
+        seq_group_metadata_list: List[SequenceGroupMetadata],
+        virtual_engine: int = 0,
+        finished_requests_ids: Optional[List[str]] = None
+    ) -> ModelInputForCPUWithSamplingMetadata:
+        """Prepare the model input based on a given sequence group, including
+        metadata for the sampling step.
+
+        """
+        model_input = self._prepare_model_input_tensors(
+            seq_group_metadata_list, finished_requests_ids)
+        # Sampling metadata is only required for the final pp group
+        generators = self.get_generators(finished_requests_ids)
+        sampling_metadata = SamplingMetadata.prepare(seq_group_metadata_list,
+                                                     model_input.seq_lens,
+                                                     model_input.query_lens,
+                                                     self.device,
+                                                     pin_memory=False,
+                                                     generators=generators)
+
+        is_prompt = (seq_group_metadata_list[0].is_prompt
+                     if seq_group_metadata_list else None)
+        return dataclasses.replace(model_input,
+                                   sampling_metadata=sampling_metadata,
+                                   virtual_engine=virtual_engine,
+                                   is_prompt=is_prompt)
+
+    @torch.no_grad()
+    def execute_model(
+        self,
+        model_input: ModelInputForCPUWithSamplingMetadata,
+        kv_caches: List[torch.Tensor],
+        intermediate_tensors: Optional[IntermediateTensors] = None,
+        num_steps: int = 1,
+        previous_hidden_states: Optional[torch.Tensor] = None,
+    ) -> Optional[List[SamplerOutput]]:
+        if num_steps > 1:
+            raise ValueError(
+                "CPU worker does not support multi-step execution.")
+
+        if self.lora_config:
+            assert model_input.lora_requests is not None
+            assert model_input.lora_mapping is not None
+            self.set_active_loras(model_input.lora_requests,
+                                  model_input.lora_mapping)
+
+        model_executable = self.model
+
+        multimodal_kwargs = {}
+        if model_input.multi_modal_kwargs is not None:
+            multimodal_kwargs = MultiModalKwargs.as_kwargs(
+                model_input.multi_modal_kwargs,
+                device=self.device,
+            )
+        execute_model_kwargs = {}
+        if previous_hidden_states is not None:
+            execute_model_kwargs.update(
+                {"previous_hidden_states": previous_hidden_states})
+
+        with set_forward_context(model_input.attn_metadata, self.vllm_config,
+                                 model_input.virtual_engine):
+            hidden_states = model_executable(
+                input_ids=model_input.input_tokens,
+                positions=model_input.input_positions,
+                intermediate_tensors=intermediate_tensors,
+                **execute_model_kwargs,
+                **multimodal_kwargs,
+            )
+
+        # Compute the logits.
+        logits = self.model.compute_logits(hidden_states,
+                                           model_input.sampling_metadata)
+
+        # Only perform sampling in the driver worker.
+        if not self.is_driver_worker:
+            return []
+
+        # Sample the next token.
+        output = self.sampler(
+            logits=logits,
+            sampling_metadata=model_input.sampling_metadata,
+        )
+        if self.return_hidden_states:
+            # we only need to pass hidden states of most recent token
+            if model_input.is_prompt:
+                output.prefill_hidden_states = hidden_states
+            output.hidden_states = hidden_states
+        return [output]
+
+    def generate_proposals(self, *args, **kwargs):
+        return self.model.generate_proposals(*args, **kwargs)

vllm/worker/cpu_pooling_model_runner.py

@@ -0,0 +1,125 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import dataclasses
+from typing import Any, Dict, List, Optional, Tuple, Type, Union
+
+import torch
+
+from vllm.forward_context import set_forward_context
+from vllm.model_executor.pooling_metadata import PoolingMetadata
+from vllm.multimodal import MultiModalKwargs
+from vllm.pooling_params import PoolingParams
+from vllm.sequence import (IntermediateTensors, PoolerOutput, SequenceData,
+                           SequenceGroupMetadata)
+from vllm.worker.cpu_model_runner import (CPUModelRunnerBase, ModelInputForCPU,
+                                          ModelInputForCPUBuilder)
+
+
+@dataclasses.dataclass(frozen=True)
+class ModelInputForCPUWithPoolingMetadata(ModelInputForCPU):
+    """
+    Used by the CPUPoolingModelRunner.
+    """
+    pooling_metadata: Optional["PoolingMetadata"] = None
+
+
+class CPUPoolingModelRunner(
+        CPUModelRunnerBase[ModelInputForCPUWithPoolingMetadata]):
+    _model_input_cls: Type[ModelInputForCPUWithPoolingMetadata] = (
+        ModelInputForCPUWithPoolingMetadata)
+    _builder_cls: Type[ModelInputForCPUBuilder] = ModelInputForCPUBuilder
+
+    @torch.inference_mode()
+    def execute_model(
+        self,
+        model_input: ModelInputForCPUWithPoolingMetadata,
+        kv_caches: List[torch.Tensor],
+        intermediate_tensors: Optional[IntermediateTensors] = None,
+        num_steps: int = 1,
+    ) -> Optional[Union[List[PoolerOutput], IntermediateTensors]]:
+        if num_steps > 1:
+            raise ValueError(
+                "CPU worker does not support multi-step execution.")
+
+        model_executable = self.model
+        cross_enc_kwargs = {}
+        if model_input.token_type_ids is not None:
+            cross_enc_kwargs["token_type_ids"] = model_input.token_type_ids
+        execute_model_kwargs = {
+            "input_ids":
+            model_input.input_tokens,
+            "positions":
+            model_input.input_positions,
+            **MultiModalKwargs.as_kwargs(
+                model_input.multi_modal_kwargs or {},
+                device=self.device,
+            ),
+            **cross_enc_kwargs,
+            "intermediate_tensors":
+            intermediate_tensors,
+        }
+
+        with set_forward_context(model_input.attn_metadata, self.vllm_config,
+                                 model_input.virtual_engine):
+            hidden_states = model_executable(**execute_model_kwargs)
+
+        # Only perform pooling in the driver worker.
+        if not self.is_driver_worker:
+            return []
+
+        return [
+            self.model.pooler(hidden_states=hidden_states,
+                              pooling_metadata=model_input.pooling_metadata)
+        ]
+
+    def make_model_input_from_broadcasted_tensor_dict(
+            self,
+            tensor_dict: Dict[str,
+                              Any]) -> ModelInputForCPUWithPoolingMetadata:
+        return ModelInputForCPUWithPoolingMetadata.from_broadcasted_tensor_dict(
+            tensor_dict,
+            attn_backend=self.attn_backend,
+        )
+
+    def prepare_model_input(
+        self,
+        seq_group_metadata_list: Optional[List[SequenceGroupMetadata]],
+        virtual_engine: int = 0,
+        finished_requests_ids: Optional[List[str]] = None
+    ) -> ModelInputForCPUWithPoolingMetadata:
+        assert seq_group_metadata_list is not None
+        model_input = self._prepare_model_input_tensors(
+            seq_group_metadata_list, finished_requests_ids)
+        # Prepare PoolingMetadata.
+        assert model_input.seq_lens is not None
+        pooling_metadata = self._prepare_pooling(seq_group_metadata_list,
+                                                 model_input.seq_lens)
+
+        return dataclasses.replace(model_input,
+                                   virtual_engine=virtual_engine,
+                                   pooling_metadata=pooling_metadata)
+
+    def _prepare_pooling(
+        self,
+        seq_group_metadata_list: List[SequenceGroupMetadata],
+        prompt_lens: List[int],
+    ) -> PoolingMetadata:
+        """Prepare PoolingMetadata for the sequence group metadata list."""
+        seq_groups: List[Tuple[List[int], PoolingParams]] = []
+        for i, seq_group_metadata in enumerate(seq_group_metadata_list):
+            seq_ids = list(seq_group_metadata.seq_data.keys())
+            pooling_params = seq_group_metadata.pooling_params
+            seq_groups.append((seq_ids, pooling_params))
+
+        seq_data: Dict[int, SequenceData] = {}
+        for seq_group_metadata in seq_group_metadata_list:
+            seq_data.update(seq_group_metadata.seq_data)
+
+        pooling_metadata = PoolingMetadata(
+            seq_groups=seq_groups,
+            seq_data=seq_data,
+            prompt_lens=prompt_lens,
+        )
+
+        return pooling_metadata

vllm/worker/cpu_worker.py

@@ -0,0 +1,452 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""A CPU worker class."""
+import os
+from importlib import util
+from typing import List, Optional, Set, Tuple, Type
+
+import torch
+import torch.distributed
+
+import vllm.envs as envs
+from vllm.attention import get_attn_backend
+from vllm.config import (CacheConfig, DeviceConfig, ModelConfig,
+                         ParallelConfig, VllmConfig)
+from vllm.distributed import (ensure_model_parallel_initialized,
+                              init_distributed_environment)
+from vllm.logger import init_logger
+from vllm.lora.request import LoRARequest
+from vllm.model_executor import set_random_seed
+from vllm.sequence import ExecuteModelRequest
+from vllm.utils import bind_kv_cache
+from vllm.worker.cpu_enc_dec_model_runner import CPUEncoderDecoderModelRunner
+from vllm.worker.cpu_model_runner import CPUModelRunner, CPUModelRunnerBase
+from vllm.worker.cpu_pooling_model_runner import CPUPoolingModelRunner
+from vllm.worker.worker_base import (LocalOrDistributedWorkerBase, WorkerBase,
+                                     WorkerInput)
+
+logger = init_logger(__name__)
+
+
+class CPUCacheEngine:
+    """Manages the KV cache for CPU backend.
+
+    This class is responsible for initializing and managing CPU KV
+    caches. It also provides methods for performing KV cache operations, such
+    as copying.
+    """
+
+    def __init__(self, cache_config: CacheConfig, model_config: ModelConfig,
+                 parallel_config: ParallelConfig,
+                 device_config: DeviceConfig) -> None:
+        assert device_config.device_type == "cpu"
+        self.cache_config = cache_config
+        self.model_config = model_config
+        self.parallel_config = parallel_config
+
+        self.head_size = model_config.get_head_size()
+        self.num_layers = model_config.get_num_layers(parallel_config)
+        self.num_heads = model_config.get_num_kv_heads(parallel_config)
+
+        self.block_size = cache_config.block_size
+        # Note: In CacheConfig, num_gpu_blocks actual is num_cpu_blocks
+        # for CPU backend, because we want to reuse KV cache management
+        # in the scheduler.
+        self.num_cpu_blocks = cache_config.num_gpu_blocks
+
+        self.dtype = CPUCacheEngine.get_kv_cache_dtype(cache_config,
+                                                       model_config)
+
+        # Get attention backend.
+        self.attn_backend = get_attn_backend(
+            self.model_config.get_head_size(),
+            self.model_config.dtype,
+            cache_config.cache_dtype,
+            self.block_size,
+            self.model_config.is_attention_free,
+            use_mla=self.model_config.use_mla,
+        )
+
+        # Initialize the cache.
+        self.cpu_cache = self._allocate_kv_cache(self.num_cpu_blocks)
+
+    def _allocate_kv_cache(
+        self,
+        num_blocks: int,
+    ) -> List[torch.Tensor]:
+        """Allocates KV cache on CPU."""
+        kv_cache_shape = self.attn_backend.get_kv_cache_shape(
+            num_blocks, self.block_size, self.num_heads, self.head_size)
+        kv_cache: List[torch.Tensor] = []
+        for _ in range(self.num_layers):
+            kv_cache.append(
+                torch.empty(kv_cache_shape, dtype=self.dtype, device="cpu"))
+        return kv_cache
+
+    def swap_in(self, src_to_dst: torch.Tensor) -> None:
+        raise NotImplementedError("Swap is not supported in CPUCacheEngine.")
+
+    def swap_out(self, src_to_dst: torch.Tensor) -> None:
+        raise NotImplementedError("Swap is not supported in CPUCacheEngine.")
+
+    def copy(self, src_to_dsts: torch.Tensor) -> None:
+        self.attn_backend.copy_blocks(self.cpu_cache, src_to_dsts)
+
+    @staticmethod
+    def get_kv_cache_dtype(cache_config: CacheConfig,
+                           model_config: ModelConfig):
+        if cache_config.cache_dtype == "auto":
+            return model_config.dtype
+        elif cache_config.cache_dtype in ["fp8", "fp8_e5m2"]:
+            return torch.float8_e5m2
+        else:
+            raise NotImplementedError(f"Unsupported KV cache type "
+                                      f"{cache_config.cache_dtype}.")
+
+    @staticmethod
+    def get_cache_block_size(
+        cache_config: CacheConfig,
+        model_config: ModelConfig,
+        parallel_config: ParallelConfig,
+    ) -> int:
+        head_size = model_config.get_head_size()
+        num_heads = model_config.get_num_kv_heads(parallel_config)
+        num_layers = model_config.get_num_layers(parallel_config)
+
+        key_cache_block = cache_config.block_size * num_heads * head_size
+        value_cache_block = key_cache_block if not model_config.use_mla else 0
+        total = num_layers * (key_cache_block + value_cache_block)
+        dtype = CPUCacheEngine.get_kv_cache_dtype(cache_config, model_config)
+        dtype_size = torch.tensor([], dtype=dtype).element_size()
+        return dtype_size * total
+
+
+class CPUWorker(LocalOrDistributedWorkerBase):
+    """A worker class that executes (a partition of) the model on a CPU socket.
+
+    Each worker is associated with a single CPU socket. The worker is 
+    responsible for maintaining the KV cache and executing the model on the 
+    CPU. In case of distributed inference, each worker is assigned a partition
+    of the model.
+    """
+
+    def __init__(
+        self,
+        vllm_config: VllmConfig,
+        local_rank: int,
+        rank: int,
+        distributed_init_method: str,
+        kv_cache_dtype: Optional[str] = "auto",
+        is_driver_worker: bool = False,
+        model_runner_cls: Optional[Type[CPUModelRunner]] = None,
+    ) -> None:
+        WorkerBase.__init__(self, vllm_config=vllm_config)
+
+        self.local_rank = local_rank
+        self.rank = rank
+        vllm_config.parallel_config.rank = rank
+
+        self.distributed_init_method = distributed_init_method
+
+        self.is_driver_worker = is_driver_worker
+        if self.is_driver_worker:
+            assert self.rank == 0, "The driver worker must have rank 0."
+
+        if self.model_config.trust_remote_code:
+            # note: lazy import to avoid importing torch before initializing
+            from vllm.utils import init_cached_hf_modules
+            init_cached_hf_modules()
+
+        # Setup OpenMP threads affinity.
+        omp_cpuids = envs.VLLM_CPU_OMP_THREADS_BIND
+        self.local_omp_cpuid = "all"
+        if omp_cpuids == "auto":
+            self.local_omp_cpuid = self.get_cpus_id_binding_based_on_numa_nodes(
+            )
+        else:
+            self.local_omp_cpuid = omp_cpuids.split("|")[rank]
+
+        # Return hidden states from target model if the draft model is an
+        # mlp_speculator
+        speculative_config = self.speculative_config
+        model_config = self.model_config
+        speculative_args = {} if speculative_config is None \
+            or (speculative_config.draft_model_config.model ==
+                model_config.model) \
+            or (speculative_config.draft_model_config.hf_config.model_type
+                not in ["medusa", "mlp_speculator", "eagle"]) \
+                    else {"return_hidden_states": True}
+        ModelRunnerClass: Type[CPUModelRunnerBase] = CPUModelRunner
+        if self.model_config.runner_type == "pooling":
+            ModelRunnerClass = CPUPoolingModelRunner
+        elif self.model_config.is_encoder_decoder:
+            ModelRunnerClass = CPUEncoderDecoderModelRunner
+        self.model_runner: CPUModelRunnerBase = ModelRunnerClass(
+            vllm_config=vllm_config,
+            kv_cache_dtype=kv_cache_dtype,
+            is_driver_worker=is_driver_worker,
+            **speculative_args,
+        )
+        if model_runner_cls is not None:
+            self.model_runner = model_runner_cls(self.model_runner)
+        # Uninitialized cache engine. Will be initialized by
+        # initialize_cache.
+        self.cache_engine: List[CPUCacheEngine]
+        # Initialize cpu_cache as pooling models don't initialize kv_caches
+        self.cpu_cache: Optional[List[List[torch.Tensor]]] = None
+
+        # Torch profiler. Enabled and configured through env vars:
+        # VLLM_TORCH_PROFILER_DIR=/path/to/save/trace
+        if envs.VLLM_TORCH_PROFILER_DIR:
+            torch_profiler_trace_dir = envs.VLLM_TORCH_PROFILER_DIR
+            logger.info("Profiling enabled. Traces will be saved to: %s",
+                        torch_profiler_trace_dir)
+            self.profiler = torch.profiler.profile(
+                activities=[
+                    torch.profiler.ProfilerActivity.CPU,
+                ],
+                with_stack=True,
+                on_trace_ready=torch.profiler.tensorboard_trace_handler(
+                    torch_profiler_trace_dir, use_gzip=True))
+        else:
+            self.profiler = None
+
+    def start_profile(self):
+        if self.profiler is None:
+            raise RuntimeError("Profiler is not enabled.")
+        self.profiler.start()
+
+    def stop_profile(self):
+        if self.profiler is None:
+            raise RuntimeError("Profiler is not enabled.")
+        self.profiler.stop()
+
+    def init_device(self) -> None:
+        if self.local_omp_cpuid != "all":
+            ret = torch.ops._C_utils.init_cpu_threads_env(self.local_omp_cpuid)
+            if ret:
+                logger.info(ret)
+
+        # Note: unique identifier for creating allreduce shared memory
+        os.environ["VLLM_DIST_IDENT"] = self.distributed_init_method.split(
+            ":")[-1]
+        self.device = torch.device("cpu")
+        self.init_distributed_environment()
+        # Set random seed.
+        set_random_seed(self.model_config.seed)
+
+    def load_model(self):
+        self.model_runner.load_model()
+
+    def determine_num_available_blocks(self) -> Tuple[int, int]:
+        """Determine the number of blocks available for the KV cache.
+
+        This determines how many KV blocks can fit into the configured CPU
+        KV cache space.
+
+        Note that since vLLM assumes a block resides on GPU if it can be
+        modified, we return num_gpu_blocks=num_cpu_blocks and num_cpu_blocks=0.
+        This allows us to reuse the scheduler of vLLM without generalizing it
+        to different devices.
+        """
+        # For CPU device, the block number will be calculated based on the
+        # cpu_kvcache_space.
+        cache_block_size = self.get_cache_block_size_bytes()
+        num_cpu_blocks = int(self.cache_config.cpu_kvcache_space_bytes //
+                             cache_block_size)
+        num_cpu_blocks = max(num_cpu_blocks, 0)
+
+        # Note: To reuse the cache management procedure,
+        # use cpu cache as 'gpu cache'.
+        num_gpu_blocks = num_cpu_blocks
+        num_cpu_blocks = 0
+        return num_gpu_blocks, num_cpu_blocks
+
+    def initialize_cache(self, num_gpu_blocks: int,
+                         num_cpu_blocks: int) -> None:
+        """Initialize the KV cache. Currently, swappable CPU memory is not
+        supported.
+
+        Since this worker does not support GPUs, we use the num_gpu_blocks to
+        determine how many non-swappable CPU blocks to allocate.
+        """
+        assert (num_cpu_blocks == 0
+                ), f"{type(self)} does not support swappable cache"
+
+        # Note: To reuse the cache management procedure,
+        # use cpu cache as 'gpu cache'.
+        num_cpu_blocks = num_gpu_blocks
+
+        self._validate_num_cpu_blocks(num_cpu_blocks)
+        self.cache_config.num_gpu_blocks = num_cpu_blocks
+        self.cache_config.num_cpu_blocks = 0
+
+        # Initialize the cache.
+        self._init_cache_engine()
+
+    def add_lora(self, lora_request: LoRARequest) -> bool:
+        return self.model_runner.add_lora(lora_request)
+
+    def remove_lora(self, lora_id: int) -> bool:
+        return self.model_runner.remove_lora(lora_id)
+
+    def pin_lora(self, lora_id: int) -> bool:
+        return self.model_runner.pin_lora(lora_id)
+
+    def list_loras(self) -> Set[int]:
+        return self.model_runner.list_loras()
+
+    def _validate_num_cpu_blocks(self, num_cpu_blocks: int) -> None:
+        """Raise errors if the num_cpu_blocks is invalid.
+        """
+        if num_cpu_blocks <= 0:
+            raise ValueError("No available memory for the cache blocks. "
+                             "Try increasing `VLLM_CPU_KVCACHE_SPACE` when "
+                             "initializing the engine.")
+
+        max_seq_len = self.cache_config.block_size * num_cpu_blocks
+        if self.model_config.max_model_len > max_seq_len:
+            raise ValueError(
+                f"The model's max seq len ({self.model_config.max_model_len}) "
+                "is larger than the maximum number of tokens that can be "
+                f"stored in KV cache ({max_seq_len}). Try increasing "
+                "`VLLM_CPU_KVCACHE_SPACE` or decreasing `max_model_len` when "
+                "initializing the engine.")
+
+    def _init_cache_engine(self) -> None:
+        self.cache_engine = [
+            CPUCacheEngine(self.cache_config, self.model_config,
+                           self.parallel_config, self.device_config)
+            for _ in range(self.parallel_config.pipeline_parallel_size)
+        ]
+        self.cpu_cache = [
+            self.cache_engine[ve].cpu_cache
+            for ve in range(self.parallel_config.pipeline_parallel_size)
+        ]
+        bind_kv_cache(self.compilation_config.static_forward_context,
+                      self.cpu_cache)
+        self.model_runner.block_size = self.cache_engine[0].block_size
+
+        assert all(
+            self.cpu_cache[ve] is not None
+            for ve in range(self.parallel_config.pipeline_parallel_size))
+
+        # Populate the cache to warmup the memory
+        for ve in range(self.parallel_config.pipeline_parallel_size):
+            for layer_cache in self.cpu_cache[ve]:
+                layer_cache.fill_(0)
+
+    @property
+    def do_metadata_broadcast(self) -> bool:
+        return self.parallel_config.tensor_parallel_size > 1
+
+    @property
+    def kv_cache(self) -> Optional[List[List[torch.Tensor]]]:
+        return self.cpu_cache
+
+    @property
+    def vocab_size(self) -> int:
+        return self.model_runner.vocab_size
+
+    @property
+    def max_model_len(self) -> int:
+        return self.model_config.max_model_len
+
+    def execute_worker(
+        self,
+        worker_input: WorkerInput,
+    ) -> None:
+        if (worker_input.blocks_to_copy is not None
+                and worker_input.blocks_to_copy.numel() > 0):
+            self.cache_engine[worker_input.virtual_engine].copy(
+                worker_input.blocks_to_copy)
+
+    @torch.inference_mode()
+    def prepare_worker_input(
+            self, execute_model_req: ExecuteModelRequest) -> WorkerInput:
+        assert execute_model_req is not None
+        virtual_engine: int = execute_model_req.virtual_engine
+        num_seq_groups: int = len(execute_model_req.seq_group_metadata_list)
+        blocks_to_copy = torch.tensor(execute_model_req.blocks_to_copy,
+                                      device="cpu",
+                                      dtype=torch.int64).view(-1, 2)
+        assert len(execute_model_req.blocks_to_swap_in) == 0
+        assert len(execute_model_req.blocks_to_swap_out) == 0
+        return WorkerInput(
+            num_seq_groups=num_seq_groups,
+            blocks_to_copy=blocks_to_copy,
+            virtual_engine=virtual_engine,
+        )
+
+    def init_distributed_environment(self) -> None:
+        """Initialize the distributed environment."""
+
+        parallel_config = self.parallel_config
+        rank = self.rank
+        distributed_init_method = self.distributed_init_method
+        init_distributed_environment(
+            world_size=parallel_config.world_size,
+            rank=rank,
+            distributed_init_method=distributed_init_method,
+            backend="gloo",
+        )
+
+        # A small all_reduce for warmup.
+        torch.distributed.all_reduce(torch.zeros(1).cpu())
+
+        ensure_model_parallel_initialized(
+            parallel_config.tensor_parallel_size,
+            parallel_config.pipeline_parallel_size)
+
+    def get_cache_block_size_bytes(self) -> int:
+        """Return the size in bytes of a single KV cache block.
+        """
+        return CPUCacheEngine.get_cache_block_size(self.cache_config,
+                                                   self.model_config,
+                                                   self.parallel_config)
+
+    def get_cpus_id_binding_based_on_numa_nodes(self) -> str:
+        """Return CPUs id binding based on NUMA nodes.
+        """
+        rank_to_cpus = self.local_omp_cpuid
+        # Setup OpenMP thread affinity based on NUMA nodes automatically
+        world_size = self.vllm_config.parallel_config.world_size
+        libnuma_found = util.find_spec("numa") is not None
+        psutil_found = util.find_spec("psutil") is not None
+        if libnuma_found and psutil_found:
+            import psutil
+            from numa import info
+            cpu_count = psutil.cpu_count(logical=False)
+            cpus_allow_list = psutil.Process().cpu_affinity()
+            numa_size = info.get_num_configured_nodes()
+            cpu_count_per_numa = cpu_count // numa_size
+            num_of_reserved_cpu = min(envs.VLLM_CPU_NUM_OF_RESERVED_CPU,
+                                      cpu_count_per_numa // 2)
+
+            # check allow node_to_cpus list
+            node_to_cpus = []
+            for i in range(numa_size):
+                node_intersect = set(
+                    info.node_to_cpus(i)).intersection(cpus_allow_list)
+                if bool(node_intersect):
+                    node_to_cpus.append(list(node_intersect))
+
+            if world_size > len(node_to_cpus):
+                logger.error(
+                    "Auto thread-binding failed due to "
+                    "world size: %d is larger than "
+                    "allowed NUMA nodes number: %d."
+                    "Please try to bind threads manually.", world_size,
+                    len(node_to_cpus))
+            else:
+                end = cpu_count_per_numa - num_of_reserved_cpu
+                rank_to_cpus_list = node_to_cpus[self.rank][:end]
+                rank_to_cpus = ','.join(str(x) for x in rank_to_cpus_list)
+                logger.info("auto thread-binding list: %s", rank_to_cpus)
+        else:
+            logger.warning(
+                "Auto thread-binding is not supported due to "
+                "the lack of package numa and psutil,"
+                "fallback to no thread-binding. To get better performance,"
+                "please try to manually bind threads.")
+        return rank_to_cpus

vllm/worker/multi_step_tpu_worker.py

@@ -0,0 +1,108 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import dataclasses
+from typing import Dict, Optional, Tuple
+
+import torch
+
+from vllm.distributed import broadcast_tensor_dict
+from vllm.sequence import ExecuteModelRequest
+from vllm.worker.tpu_model_runner import ModelInputForTPU
+from vllm.worker.tpu_worker import TPUWorker
+from vllm.worker.worker_base import WorkerInput
+
+
+class MultiStepTPUWorker(TPUWorker):
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.cached_model_input: Optional[ModelInputForTPU] = None
+
+    def _get_driver_input_and_broadcast(
+        self, execute_model_req: ExecuteModelRequest
+    ) -> Tuple[ModelInputForTPU, WorkerInput, Dict[str, torch.Tensor]]:
+        assert self.is_driver_worker
+        assert execute_model_req.virtual_engine == 0
+
+        is_first_multi_step = execute_model_req.is_first_multi_step
+        is_last_step = execute_model_req.is_last_step
+        if is_first_multi_step:
+            worker_input: WorkerInput = self.prepare_worker_input(
+                execute_model_req=execute_model_req)
+            worker_input = dataclasses.replace(
+                worker_input,
+                num_steps=execute_model_req.num_lookahead_slots + 1)
+            model_input: ModelInputForTPU = (
+                self.model_runner.prepare_model_input(
+                    execute_model_req.seq_group_metadata_list,
+                    execute_model_req.virtual_engine,
+                    execute_model_req.finished_requests_ids))
+
+            if execute_model_req.async_callback:
+                model_input = dataclasses.replace(
+                    model_input,
+                    async_callback=execute_model_req.async_callback)
+        else:
+            assert self.cached_model_input is not None
+            model_input = self.cached_model_input
+            worker_input = WorkerInput()
+        model_input = dataclasses.replace(
+            model_input,
+            is_first_multi_step=is_first_multi_step,
+            is_last_step=is_last_step)
+
+        if self.do_metadata_broadcast:
+            if is_first_multi_step:
+                broadcast_data = worker_input.as_broadcastable_tensor_dict()
+                broadcast_data.update(
+                    model_input.as_broadcastable_tensor_dict())
+                broadcast_tensor_dict(broadcast_data, src=0)
+            else:
+                broadcast_data = {
+                    "is_first_multi_step": is_first_multi_step,
+                    "is_last_step": is_last_step,
+                }
+                broadcast_tensor_dict(broadcast_data, src=0)
+
+        # Retuning empty dict here to keep this compatible with
+        # `LocalOrDistributedWorkerBase._get_driver_input_and_broadcast`
+        return model_input, worker_input, {}
+
+    def prepare_input(
+        self,
+        execute_model_req: Optional[ExecuteModelRequest] = None,
+    ) -> Optional[Tuple[ModelInputForTPU, WorkerInput, Dict[str,
+                                                            torch.Tensor]]]:
+        if self.is_driver_worker:
+            if execute_model_req is None:
+                if self.do_metadata_broadcast:
+                    broadcast_tensor_dict({}, src=0)
+                return None
+
+            model_input, worker_input, _ = self._get_driver_input_and_broadcast(
+                execute_model_req)
+            if model_input.is_first_multi_step:
+                self.cached_model_input = model_input
+            return model_input, worker_input, {}
+        else:
+            broadcast_data = broadcast_tensor_dict(src=0)
+            if not broadcast_data:
+                return None
+
+            if len(broadcast_data) == 2:
+                assert self.cached_model_input is not None
+                self.cached_model_input = dataclasses.replace(
+                    self.cached_model_input,
+                    is_first_multi_step=broadcast_data["is_first_multi_step"],
+                    is_last_step=broadcast_data["is_last_step"])
+                empty_worker_input = WorkerInput()
+                return self.cached_model_input, empty_worker_input, {}
+
+            worker_input = WorkerInput.from_broadcasted_tensor_dict(
+                broadcast_data)
+            model_input = (
+                self.model_runner.
+                make_model_input_from_broadcasted_tensor_dict(broadcast_data))
+            self.cached_model_input = model_input
+            return model_input, worker_input, {}

vllm/worker/tpu_model_runner.py

@@ -0,0 +1,909 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import enum
+import time
+from dataclasses import dataclass
+from typing import (TYPE_CHECKING, Any, Callable, Dict, List, Optional, Tuple,
+                    Type, Union)
+from unittest.mock import patch
+
+import numpy as np
+import torch
+import torch.nn as nn
+import torch_xla.core.xla_model as xm
+import torch_xla.runtime as xr
+
+from vllm.attention import AttentionMetadata, get_attn_backend
+from vllm.config import VllmConfig
+from vllm.forward_context import get_forward_context, set_forward_context
+from vllm.logger import init_logger
+from vllm.model_executor.layers.sampler import SamplerOutput
+from vllm.model_executor.model_loader import get_model
+from vllm.model_executor.sampling_metadata import SamplingMetadata
+from vllm.sequence import (CompletionSequenceGroupOutput, IntermediateTensors,
+                           Logprob, SequenceGroupMetadata, SequenceOutput)
+from vllm.worker.model_runner_base import (
+    ModelRunnerBase, ModelRunnerInputBase,
+    _add_attn_metadata_broadcastable_dict,
+    _init_attn_metadata_from_tensor_dict)
+
+if TYPE_CHECKING:
+    from vllm.attention.backends.abstract import AttentionBackend
+
+logger = init_logger(__name__)
+
+# Here we utilize the behavior that out-of-bound index is ignored.
+# FIXME(woosuk): Find a more reliable way to prevent possible bugs.
+_PAD_SLOT_ID = 1_000_000_000
+# FIXME(woosuk): Temporarily disabled top-p sampling since it's too slow.
+_ENABLE_TOP_P = False
+# FIXME(woosuk): A temporary hack to support `n > 1`.
+# This can significantly affect the performance if too large.
+_MAX_NUM_SAMPLES = 128
+
+
+class ExecutionMode(enum.Enum):
+    PREFILL = enum.auto()
+    DECODE = enum.auto()
+    PREFIX_PREFILL = enum.auto()
+
+    def is_prefill(self) -> bool:
+        return self in (ExecutionMode.PREFILL, ExecutionMode.PREFIX_PREFILL)
+
+
+@dataclass(frozen=True)
+class ModelInputForTPU(ModelRunnerInputBase):
+    token_ids: torch.Tensor
+    position_ids: torch.Tensor
+    attn_metadata: AttentionMetadata
+    input_lens: torch.Tensor
+    t: torch.Tensor
+    p: torch.Tensor
+    num_samples: int
+    n: List[int]
+    seq_groups: List[List[int]]
+    is_first_multi_step: bool = True
+    is_last_step: bool = True
+    virtual_engine: int = 0
+    async_callback: Optional[Callable] = None
+
+    def as_broadcastable_tensor_dict(
+            self) -> Dict[str, Union[int, torch.Tensor]]:
+        tensor_dict = {
+            "token_ids": self.token_ids,
+            "position_ids": self.position_ids,
+            "input_lens": self.input_lens,
+            "t": self.t,
+            "p": self.p,
+            "num_samples": self.num_samples,
+            "n": self.n,
+            "seq_groups": self.seq_groups,
+            "is_first_multi_step": self.is_first_multi_step,
+            "is_last_step": self.is_last_step,
+            "virtual_engine": self.virtual_engine,
+        }
+        _add_attn_metadata_broadcastable_dict(tensor_dict, self.attn_metadata)
+        return tensor_dict
+
+    @classmethod
+    def from_broadcasted_tensor_dict(
+        cls: Type["ModelInputForTPU"],
+        tensor_dict: Dict[str, Any],
+        attn_backend: Optional["AttentionBackend"] = None,
+    ) -> "ModelInputForTPU":
+        if attn_backend is not None:
+            tensor_dict = _init_attn_metadata_from_tensor_dict(
+                attn_backend, tensor_dict)
+        return cls(**tensor_dict)
+
+
+class TPUModelRunner(ModelRunnerBase[ModelInputForTPU]):
+
+    def __init__(
+        self,
+        vllm_config: VllmConfig,
+        is_driver_worker: bool = False,
+    ):
+        ModelRunnerBase.__init__(self, vllm_config=vllm_config)
+        self.is_driver_worker = is_driver_worker
+
+        self.block_size = self.cache_config.block_size
+        self.max_num_blocks_per_seq = (self.model_config.max_model_len //
+                                       self.block_size)
+        self.block_tables = np.zeros(
+            (self.scheduler_config.max_num_seqs, self.max_num_blocks_per_seq),
+            dtype=np.int32)
+        self.attn_backend = get_attn_backend(
+            self.model_config.get_head_size(),
+            self.model_config.dtype,
+            self.cache_config.cache_dtype,
+            self.block_size,
+            self.model_config.is_attention_free,
+            False,
+        )
+        self.cached_step_outputs: List[torch.Tensor] = []
+
+        smem_size = 512 * 1024
+        block_table_size = 4 * self.block_tables.size
+        if block_table_size >= smem_size:
+            logger.warning(
+                "The max_model_len (%d) is too large. This may degrade the "
+                "performance due to the insufficient smem size. Consider "
+                "setting --max-model-len to a smaller value, like %d.",
+                self.model_config.max_model_len,
+                self.model_config.max_model_len /
+                (block_table_size / smem_size))
+
+    def load_model(self) -> None:
+        self.device = self.device_config.device
+
+        # NOTE(woosuk): While the executor assigns the TP ranks to the worker
+        # process, the ranks can be different from the ranks internally assigned
+        # by the xm runtime. Therefore, there is a mismatch in the rank
+        # assignment between the gloo (cpu) runtime and the xm (tpu) runtime.
+        # This is not a problem in linear layers because all-reduce is
+        # rank-agnostic. However, it matters for all-gather as the ranks
+        # determine the order of concatenating the output tensors.
+        # As a workaround, we use the xm's rank assignment only when loading
+        # the embedding weights.
+        xm_tp_rank = xr.global_ordinal()
+        with patch(
+                "vllm.model_executor.layers.vocab_parallel_embedding."
+                "get_tensor_model_parallel_rank",
+                return_value=xm_tp_rank):
+            model = get_model(vllm_config=self.vllm_config)
+        model = model.eval()
+        xm.wait_device_ops()
+        model = ModelWrapper(model)
+        self.model = torch.compile(model,
+                                   backend="openxla",
+                                   fullgraph=True,
+                                   dynamic=False)
+
+    def get_model(self) -> nn.Module:
+        return self.model.model
+
+    def _dummy_run(
+        self,
+        batch_size: int,
+        seq_len: int,
+        kv_caches: List[Tuple[torch.Tensor, torch.Tensor]],
+        exec_mode: ExecutionMode,
+    ) -> None:
+        exec_mode = ExecutionMode(exec_mode)
+        if exec_mode.is_prefill():
+            seq_len = (seq_len + 15) // 16 * 16
+            token_ids = torch.zeros((batch_size, seq_len),
+                                    dtype=torch.int32,
+                                    device=self.device)
+            position_ids = torch.zeros((batch_size, seq_len),
+                                       dtype=torch.int32,
+                                       device=self.device)
+            slot_mapping = torch.zeros((batch_size, seq_len),
+                                       dtype=torch.int64,
+                                       device=self.device)
+            input_lens = torch.ones((batch_size, ),
+                                    dtype=torch.int32,
+                                    device=self.device)
+            if exec_mode == ExecutionMode.PREFILL:
+                attn_metadata = self.attn_backend.make_metadata(
+                    num_prefills=batch_size,
+                    num_prefill_tokens=batch_size * seq_len,
+                    num_decode_tokens=0,
+                    slot_mapping=slot_mapping,
+                    multi_modal_placeholder_index_maps=None,
+                    enable_kv_scales_calculation=False,
+                    block_tables=None,
+                    context_lens=None,
+                    effective_query_lens=None,
+                )
+            else:
+                context_lens = torch.ones((batch_size, ),
+                                          dtype=torch.int32,
+                                          device=self.device)
+                block_tables = torch.tensor(self.block_tables[:batch_size],
+                                            dtype=torch.int32,
+                                            device=self.device)
+                effective_query_lens = torch.ones_like(context_lens)
+                attn_metadata = self.attn_backend.make_metadata(
+                    num_prefills=batch_size,
+                    num_prefill_tokens=batch_size * seq_len,
+                    num_decode_tokens=0,
+                    slot_mapping=slot_mapping,
+                    multi_modal_placeholder_index_maps=None,
+                    enable_kv_scales_calculation=False,
+                    block_tables=block_tables,
+                    context_lens=context_lens,
+                    effective_query_lens=effective_query_lens,
+                )
+        else:
+            assert seq_len == 1
+            token_ids = torch.zeros((batch_size, seq_len),
+                                    dtype=torch.int32,
+                                    device=self.device)
+            position_ids = torch.zeros((batch_size, seq_len),
+                                       dtype=torch.int32,
+                                       device=self.device)
+            slot_mapping = torch.zeros((batch_size, seq_len),
+                                       dtype=torch.int64,
+                                       device=self.device)
+            block_tables = torch.zeros(
+                (batch_size, self.max_num_blocks_per_seq),
+                dtype=torch.int32,
+                device=self.device)
+            context_lens = torch.ones((batch_size, ),
+                                      dtype=torch.int32,
+                                      device=self.device)
+            input_lens = torch.ones((batch_size, ),
+                                    dtype=torch.int32,
+                                    device=self.device)
+            attn_metadata = self.attn_backend.make_metadata(
+                num_prefills=0,
+                num_prefill_tokens=0,
+                num_decode_tokens=batch_size * seq_len,
+                slot_mapping=slot_mapping,
+                multi_modal_placeholder_index_maps=None,
+                enable_kv_scales_calculation=False,
+                block_tables=block_tables,
+                context_lens=context_lens,
+            )
+        t = torch.ones((batch_size, ), dtype=torch.float32, device=self.device)
+        p = torch.ones((batch_size, ), dtype=torch.float32, device=self.device)
+        num_samples = _MAX_NUM_SAMPLES if exec_mode.is_prefill() else 1
+
+        # NOTE(woosuk): There are two stages of compilation: torch.compile and
+        # XLA compilation. Using `mark_dynamic` can reduce the torch.compile
+        # overhead by reusing the FX graph for different shapes.
+        # However, the XLA graph will still require static shapes and needs to
+        # be re-compiled for every different shapes. This overhead is inevitable
+        # in the first run, but can be skipped afterwards as we cache the XLA
+        # graphs in the disk (VLLM_XLA_CACHE_PATH).
+        if exec_mode.is_prefill():
+            # Prefll
+            torch._dynamo.mark_dynamic(token_ids, 1)
+            torch._dynamo.mark_dynamic(position_ids, 1)
+            torch._dynamo.mark_dynamic(attn_metadata.slot_mapping, 1)
+        else:
+            # Decode
+            torch._dynamo.mark_dynamic(token_ids, 0)
+            torch._dynamo.mark_dynamic(position_ids, 0)
+            torch._dynamo.mark_dynamic(input_lens, 0)
+            torch._dynamo.mark_dynamic(attn_metadata.slot_mapping, 0)
+            torch._dynamo.mark_dynamic(attn_metadata.context_lens, 0)
+            torch._dynamo.mark_dynamic(attn_metadata.block_tables, 0)
+            torch._dynamo.mark_dynamic(t, 0)
+            torch._dynamo.mark_dynamic(p, 0)
+        # Dummy run.
+        with set_forward_context(attn_metadata, self.vllm_config, 0):
+            self.model(token_ids, position_ids, input_lens, t, p, num_samples,
+                       kv_caches)
+
+    def warmup_model(
+        self,
+        kv_caches: List[Tuple[torch.Tensor, torch.Tensor]],
+    ) -> None:
+        # Prefill
+        logger.info("Compiling the model with different input shapes...")
+        start = time.time()
+        for batch_size in [1]:
+            seq_len = 16
+            while seq_len <= self.model_config.max_model_len:
+                self._dummy_run(batch_size,
+                                seq_len,
+                                kv_caches,
+                                exec_mode=ExecutionMode.PREFILL)
+                xm.wait_device_ops()
+                logger.info("batch_size: %d, seq_len: %d", batch_size, seq_len)
+                num_tokens = batch_size * seq_len
+                if num_tokens >= self.scheduler_config.max_num_batched_tokens:
+                    break
+                seq_len = seq_len * 2
+
+        end = time.time()
+        logger.info("Compilation for prefill done in %.2f s.", end - start)
+
+        # Prefix prefill
+        if self.cache_config.enable_prefix_caching:
+            logger.info("Compiling the model with different input shapes for "
+                        "prefix prefill...")
+            start = time.time()
+            for batch_size in [1]:
+                seq_len = 16
+                while seq_len <= self.model_config.max_model_len:
+                    self._dummy_run(batch_size,
+                                    seq_len,
+                                    kv_caches,
+                                    exec_mode=ExecutionMode.PREFIX_PREFILL)
+                    xm.wait_device_ops()
+                    logger.info("batch_size: %d, seq_len: %d", batch_size,
+                                seq_len)
+                    num_tokens = batch_size * seq_len
+                    if (num_tokens
+                            >= self.scheduler_config.max_num_batched_tokens):
+                        break
+                    seq_len = seq_len * 2
+            end = time.time()
+            logger.info("Compilation for prefix prefill done in %.2f s.",
+                        end - start)
+
+        # Decode
+        start = time.time()
+        seq_len = 1
+        batch_size = 8  # Must be in sync with _get_padded_batch_size()
+        while True:
+            self._dummy_run(batch_size,
+                            seq_len,
+                            kv_caches,
+                            exec_mode=ExecutionMode.DECODE)
+            xm.wait_device_ops()
+            logger.info("batch_size: %d, seq_len: %d", batch_size, seq_len)
+
+            if batch_size >= self.scheduler_config.max_num_seqs:
+                break
+            batch_size = batch_size + 16 if batch_size >= 16 else batch_size * 2
+
+        end = time.time()
+        logger.info("Compilation for decode done in %.2f s.", end - start)
+
+    def _prepare_prompt(
+        self,
+        seq_group_metadata_list: List[SequenceGroupMetadata],
+    ) -> Tuple[torch.Tensor, torch.Tensor, AttentionMetadata, torch.Tensor]:
+        assert len(seq_group_metadata_list) > 0
+        input_tokens: List[int] = []
+        input_positions: List[int] = []
+        prompt_lens: List[int] = []
+        context_lens: List[int] = []
+        slot_mapping: List[int] = []
+
+        for batch_idx, seq_group_metadata in enumerate(
+                seq_group_metadata_list):
+            assert seq_group_metadata.is_prompt
+            seq_ids = list(seq_group_metadata.seq_data.keys())
+            assert len(seq_ids) == 1
+            seq_id = seq_ids[0]
+
+            seq_data = seq_group_metadata.seq_data[seq_id]
+            # Could include output tokens when a request is preempted.
+            prompt_tokens = seq_data.get_token_ids()
+            seq_len = len(prompt_tokens)
+
+            num_computed_blocks = len(seq_group_metadata.computed_block_nums)
+            num_computed_tokens = num_computed_blocks * self.block_size
+            if num_computed_tokens > 0:
+                prompt_tokens = prompt_tokens[num_computed_tokens:]
+                context_lens.append(seq_len)
+            else:
+                context_lens.append(0)
+
+            prompt_len = len(prompt_tokens)
+            prompt_lens.append(prompt_len)
+
+            input_tokens.extend(prompt_tokens)
+            input_positions.extend(range(num_computed_tokens, seq_len))
+
+            assert seq_group_metadata.block_tables is not None
+            block_table = seq_group_metadata.block_tables[seq_id]
+            for i in range(num_computed_tokens, seq_len):
+                block_number = block_table[i // self.block_size]
+                block_offset = i % self.block_size
+                slot = block_number * self.block_size + block_offset
+                slot_mapping.append(slot)
+            if num_computed_tokens > 0:
+                self.block_tables[batch_idx, :len(block_table)] = block_table
+
+            # Add paddings to EACH prompt to the smallest power of 2 that is
+            # greater than or equal to the prompt length.
+            # We pad the seq_len to reduce the compilation overhead.
+            # We execute each prompt individually (i.e., with batch_size 1)
+            # because the FlashAttention kernel does not support ragged inputs.
+            # TODO(woosuk): Use SplashAttention to support ragged inputs.
+            padded_prompt_len = _get_padded_prefill_len(prompt_len)
+            num_paddings = padded_prompt_len - prompt_len
+            input_tokens += [0] * num_paddings
+            input_positions += [0] * num_paddings
+            slot_mapping += [_PAD_SLOT_ID] * num_paddings
+
+        assert len(prompt_lens) > 0
+        num_prefills = len(prompt_lens)
+        input_tokens = torch.tensor(input_tokens,
+                                    dtype=torch.int32,
+                                    device="cpu")
+        input_positions = torch.tensor(input_positions,
+                                       dtype=torch.int32,
+                                       device="cpu")
+        slot_mapping = torch.tensor(slot_mapping,
+                                    dtype=torch.int64,
+                                    device="cpu")
+        prompt_lens = torch.tensor(prompt_lens,
+                                   dtype=torch.int32,
+                                   device="cpu")
+        context_lens = torch.tensor(context_lens,
+                                    dtype=torch.int32,
+                                    device="cpu")
+        block_tables = torch.tensor(self.block_tables[:num_prefills],
+                                    dtype=torch.int32,
+                                    device="cpu")
+        attn_metadata = self.attn_backend.make_metadata(
+            num_prefills=num_prefills,
+            num_prefill_tokens=0,  # NOTE: This is not used.
+            num_decode_tokens=0,
+            slot_mapping=slot_mapping,
+            multi_modal_placeholder_index_maps=None,
+            enable_kv_scales_calculation=False,
+            block_tables=block_tables,
+            context_lens=context_lens,
+            effective_query_lens=prompt_lens,
+        )
+        return input_tokens, input_positions, attn_metadata, prompt_lens
+
+    def _prepare_decode(
+        self,
+        seq_group_metadata_list: List[SequenceGroupMetadata],
+    ) -> Tuple[torch.Tensor, torch.Tensor, AttentionMetadata, torch.Tensor]:
+        assert len(seq_group_metadata_list) > 0
+        input_tokens: List[List[int]] = []
+        input_positions: List[List[int]] = []
+        slot_mapping: List[List[int]] = []
+        context_lens: List[int] = []
+
+        batch_idx = 0
+        for seq_group_metadata in seq_group_metadata_list:
+            assert not seq_group_metadata.is_prompt
+            seq_ids = list(seq_group_metadata.seq_data.keys())
+            for seq_id in seq_ids:
+                seq_data = seq_group_metadata.seq_data[seq_id]
+                generation_token = seq_data.get_last_token_id()
+                input_tokens.append([generation_token])
+
+                seq_len = seq_data.get_len()
+                position = seq_len - 1
+                input_positions.append([position])
+                context_lens.append(seq_len)
+
+                assert seq_group_metadata.block_tables is not None
+                block_table = seq_group_metadata.block_tables[seq_id]
+                self.block_tables[batch_idx, :len(block_table)] = block_table
+                batch_idx += 1
+
+                block_number = block_table[position // self.block_size]
+                block_offset = position % self.block_size
+                slot = block_number * self.block_size + block_offset
+                slot_mapping.append([slot])
+
+        batch_size = _get_padded_batch_size(batch_idx)
+        num_paddings = batch_size - batch_idx
+        input_tokens = input_tokens + [[0]] * num_paddings
+        input_positions = input_positions + [[0]] * num_paddings
+        slot_mapping = slot_mapping + [[_PAD_SLOT_ID]] * num_paddings
+        context_lens = context_lens + [0] * num_paddings
+
+        input_tokens = torch.tensor(input_tokens,
+                                    dtype=torch.int32,
+                                    device="cpu")
+        input_positions = torch.tensor(input_positions,
+                                       dtype=torch.int32,
+                                       device="cpu")
+        slot_mapping = torch.tensor(slot_mapping,
+                                    dtype=torch.int64,
+                                    device="cpu")
+        context_lens = torch.tensor(context_lens,
+                                    dtype=torch.int32,
+                                    device="cpu")
+        block_tables = torch.tensor(self.block_tables[:batch_size],
+                                    dtype=torch.int32,
+                                    device="cpu")
+        input_lens = torch.tensor([1] * batch_size,
+                                  dtype=torch.int32,
+                                  device="cpu")
+        attn_metadata = self.attn_backend.make_metadata(
+            num_prefills=0,
+            num_prefill_tokens=0,
+            num_decode_tokens=batch_size,
+            slot_mapping=slot_mapping,
+            multi_modal_placeholder_index_maps=None,
+            enable_kv_scales_calculation=False,
+            block_tables=block_tables,
+            context_lens=context_lens,
+        )
+        return input_tokens, input_positions, attn_metadata, input_lens
+
+    def _prepare_sample(
+        self,
+        seq_group_metadata_list: List[SequenceGroupMetadata],
+        padded_batch_size: int,
+    ) -> Tuple[torch.Tensor, torch.Tensor, List[int]]:
+        assert len(seq_group_metadata_list) > 0
+        t = []
+        p = []
+        n = []
+        for seq_group_metadata in seq_group_metadata_list:
+            sampling_params = seq_group_metadata.sampling_params
+            t.append(sampling_params.temperature)
+            if sampling_params.top_p != 1 and not _ENABLE_TOP_P:
+                raise NotImplementedError(
+                    "Top-p sampling is currently disabled for the TPU backend "
+                    "due to performance issues.")
+            p.append(sampling_params.top_p)
+            if sampling_params.top_k > 0:
+                raise NotImplementedError(
+                    "Top-k sampling is currently disabled for the TPU backend "
+                    "due to performance issues.")
+            if sampling_params.n > _MAX_NUM_SAMPLES:
+                raise NotImplementedError(
+                    f"Best of > {_MAX_NUM_SAMPLES} is not supported by the TPU "
+                    "backend.")
+            n.append(sampling_params.n)
+            if sampling_params.logprobs is not None:
+                raise NotImplementedError(
+                    "logprobs is not currently supported by the TPU backend.")
+            if sampling_params.prompt_logprobs is not None:
+                raise NotImplementedError(
+                    "prompt_logprobs is not currently supported by the TPU "
+                    "backend.")
+
+            # Repeat the sampling params if the seq group has multiple seqs.
+            num_seqs = len(seq_group_metadata.seq_data)
+            t += [t[-1]] * (num_seqs - 1)
+            p += [p[-1]] * (num_seqs - 1)
+            n += [n[-1]] * (num_seqs - 1)
+
+        num_paddings = padded_batch_size - len(t)
+        t += [1.0] * num_paddings
+        p += [1.0] * num_paddings
+
+        t = torch.tensor(t, dtype=torch.float32, device="cpu")
+        p = torch.tensor(p, dtype=torch.float32, device="cpu")
+        return t, p, n
+
+    def prepare_model_input(
+        self,
+        seq_group_metadata_list: List[SequenceGroupMetadata],
+        virtual_engine: int = 0,
+        finished_requests_ids: Optional[List[str]] = None,
+    ) -> ModelInputForTPU:
+        del finished_requests_ids  # Unused.
+        assert virtual_engine == 0
+        assert len(seq_group_metadata_list) > 0
+        # NOTE: We assume that all sequences in the group are all prompts or
+        # all decodes.
+        is_prompt = seq_group_metadata_list[0].is_prompt
+        if is_prompt:
+            inputs = self._prepare_prompt(seq_group_metadata_list)
+        else:
+            inputs = self._prepare_decode(seq_group_metadata_list)
+        input_tokens, input_positions, attn_metadata, input_lens = inputs
+        padded_batch_size = input_tokens.shape[0]
+        t, p, n = self._prepare_sample(seq_group_metadata_list,
+                                       padded_batch_size)
+        num_samples = _MAX_NUM_SAMPLES if is_prompt else 1
+
+        seq_groups = [
+            list(metadata.seq_data.keys())
+            for metadata in seq_group_metadata_list
+        ]
+        return ModelInputForTPU(input_tokens, input_positions, attn_metadata,
+                                input_lens, t, p, num_samples, n, seq_groups)
+
+    def make_model_input_from_broadcasted_tensor_dict(
+            self, tensor_dict: Dict[str, Any]) -> ModelInputForTPU:
+        model_input = ModelInputForTPU.from_broadcasted_tensor_dict(
+            tensor_dict, attn_backend=self.attn_backend)
+        return model_input
+
+    @torch.no_grad()
+    def execute_model(
+        self,
+        model_input: ModelInputForTPU,
+        kv_caches: Optional[List[Any]],
+        intermediate_tensors: Optional[IntermediateTensors] = None,
+        num_steps: int = 1,
+    ) -> List[SamplerOutput]:
+        assert intermediate_tensors is None
+        if not model_input.is_first_multi_step:
+            if not model_input.is_last_step:
+                return []
+
+            use_async_out_proc = model_input.async_callback is not None
+            sampler_outputs = []
+            num_outputs = len(self.cached_step_outputs)
+            for i in range(num_outputs):
+                next_token_ids = self.cached_step_outputs.pop(0)
+                next_token_ids = next_token_ids.cpu().tolist()
+                sampler_output = _make_decode_output(next_token_ids,
+                                                     model_input.seq_groups)
+                sampler_outputs.append(sampler_output)
+
+                if i < num_outputs - 1 and use_async_out_proc:
+                    assert model_input.async_callback is not None
+                    ctx = model_input.async_callback.keywords[  # type: ignore
+                        "ctx"]
+                    ctx.append_output(
+                        outputs=[sampler_output],
+                        seq_group_metadata_list=ctx.seq_group_metadata_list,
+                        scheduler_outputs=ctx.scheduler_outputs,
+                        is_async=False,
+                        is_last_step=False,
+                        is_first_step_output=i == 0)
+                    model_input.async_callback()
+            if use_async_out_proc:
+                return [sampler_outputs[-1]]
+            else:
+                return sampler_outputs
+
+        is_prompt = model_input.attn_metadata.num_prefills > 0
+        if is_prompt:
+            assert num_steps == 1
+            # NOTE(woosuk): Since the FlashAttention kernel does not support
+            # ragged inputs, we split the prompts into different batches and
+            # process them separately. This is a temporary hack that should be
+            # optimized by using SplashAttention.
+            orig_slot_mapping = model_input.attn_metadata.slot_mapping
+            orig_block_tables = model_input.attn_metadata.block_tables
+            orig_context_lens = model_input.attn_metadata.context_lens
+            orig_effective_query_lens = \
+                model_input.attn_metadata.effective_query_lens
+            batch_size = model_input.input_lens.shape[0]
+            start_idx = 0
+            next_token_ids = []
+            for i in range(batch_size):
+                # Get the actual prefill_len.
+                prefill_len = model_input.input_lens[i:i + 1].item()
+                prefill_len = _get_padded_prefill_len(prefill_len)
+                end_idx = start_idx + prefill_len
+
+                token_ids = model_input.token_ids[None, start_idx:end_idx].to(
+                    self.device)
+                position_ids = model_input.position_ids[None,
+                                                        start_idx:end_idx].to(
+                                                            self.device)
+                attn_metadata = model_input.attn_metadata
+                attn_metadata.num_prefills = 1
+                attn_metadata.slot_mapping = orig_slot_mapping[
+                    None, start_idx:end_idx].to(self.device)
+                if orig_context_lens[i].item() > 0:
+                    attn_metadata.context_lens = orig_context_lens[i:i + 1].to(
+                        self.device)
+                    attn_metadata.block_tables = orig_block_tables[
+                        i].unsqueeze(0).to(self.device)
+                    attn_metadata.effective_query_lens = \
+                        orig_effective_query_lens[i:i + 1].to(self.device)
+                else:
+                    attn_metadata.context_lens = None
+                    attn_metadata.block_tables = None
+                    attn_metadata.effective_query_lens = None
+                input_lens = model_input.input_lens[i:i + 1].to(self.device)
+                t = model_input.t[i:i + 1].to(self.device)
+                p = model_input.p[i:i + 1].to(self.device)
+                with set_forward_context(model_input.attn_metadata,
+                                         self.vllm_config,
+                                         model_input.virtual_engine):
+                    output_token_ids = self.model(token_ids, position_ids,
+                                                  input_lens, t, p,
+                                                  model_input.num_samples,
+                                                  kv_caches)
+                next_token_ids.append(output_token_ids[0])
+                start_idx = end_idx
+
+            if model_input.async_callback is not None:
+                model_input.async_callback()
+            # Retrieve the outputs to CPU.
+            next_token_ids = [
+                output_token_ids.cpu().tolist()
+                for output_token_ids in next_token_ids
+            ]
+
+            # NOTE(woosuk): Minimal code to construct the sampler outputs.
+            # The TPU backend does not reuse the sampler, since the TPU backend
+            # does not support advanced sampling parameters such as logprobs.
+            zero_logprob = Logprob(0.0)
+            sampler_outputs = []
+            for i, seq_group in enumerate(model_input.seq_groups):
+                seq_ids = seq_group
+                assert len(seq_ids) == 1
+                seq_id = seq_ids[0]
+                seq_outputs = []
+                for j in range(model_input.n[i]):
+                    next_token_id = next_token_ids[i][j]
+                    seq_outputs.append(
+                        SequenceOutput(seq_id, next_token_id,
+                                       {next_token_id: zero_logprob}))
+                sampler_outputs.append(
+                    CompletionSequenceGroupOutput(seq_outputs, None))
+            return [SamplerOutput(sampler_outputs)]
+        else:
+            token_ids = model_input.token_ids.to(self.device)
+            position_ids = model_input.position_ids.to(self.device)
+            attn_metadata = model_input.attn_metadata
+            attn_metadata.slot_mapping = attn_metadata.slot_mapping.to(
+                self.device)
+            attn_metadata.block_tables = attn_metadata.block_tables.to(
+                self.device)
+            attn_metadata.context_lens = attn_metadata.context_lens.to(
+                self.device)
+            t = model_input.t.to(self.device)
+            p = model_input.p.to(self.device)
+            input_lens = model_input.input_lens.to(self.device)
+            for i in range(num_steps):
+                slot_mapping = attn_metadata.slot_mapping
+                with set_forward_context(model_input.attn_metadata,
+                                         self.vllm_config,
+                                         model_input.virtual_engine):
+                    output_token_ids = self.model(token_ids, position_ids,
+                                                  input_lens, t, p,
+                                                  model_input.num_samples,
+                                                  kv_caches)
+                self.cached_step_outputs.append(output_token_ids)
+
+                if i < num_steps - 1:
+                    # Prepare the inputs for the next step.
+                    token_ids = output_token_ids.unsqueeze(dim=1).int()
+                    position_ids = position_ids + 1
+                    attn_metadata.context_lens = attn_metadata.context_lens + 1
+
+                    block_tables = attn_metadata.block_tables
+                    block_number = block_tables.gather(
+                        1,
+                        position_ids.long() // self.block_size)
+                    block_offset = position_ids % self.block_size
+
+                    is_padding = slot_mapping == _PAD_SLOT_ID
+                    slot_mapping = block_number * self.block_size + block_offset
+                    slot_mapping = slot_mapping.long()
+                    slot_mapping = torch.where(is_padding, _PAD_SLOT_ID,
+                                               slot_mapping)
+                    attn_metadata.slot_mapping = slot_mapping
+
+            if model_input.async_callback is not None:
+                model_input.async_callback()
+
+            if num_steps > 1:
+                return []
+            # Retrieve the outputs to CPU.
+            next_token_ids = self.cached_step_outputs.pop(0)
+            next_token_ids = next_token_ids.cpu().tolist()
+            sampler_output = _make_decode_output(next_token_ids,
+                                                 model_input.seq_groups)
+            return [sampler_output]
+
+
+class ModelWrapper(nn.Module):
+
+    def __init__(self, model: nn.Module):
+        super().__init__()
+        self.model = model
+
+    def forward(
+        self,
+        token_ids: torch.Tensor,
+        position_ids: torch.Tensor,
+        input_lens: torch.Tensor,
+        t: torch.Tensor,
+        p: torch.Tensor,
+        num_samples: int,
+        kv_caches: List[Tuple[torch.Tensor, torch.Tensor]],
+    ) -> torch.Tensor:
+        """Executes the forward pass of the model and samples the next token.
+
+        Args:
+            token_ids: The input token IDs of shape [batch_size, seq_len].
+            position_ids: The input position IDs of shape [batch_size, seq_len].
+            input_lens: The actual input lengths of shape [batch_size].
+            t: The sampling temperature of shape [batch_size].
+            p: The top-p probability of shape [batch_size].
+            num_samples: Number of samples to draw from each logits vector.
+            kv_caches: The key and value caches. They can be None during the
+                memory profiling at initialization.
+        """
+        batch_size, seq_len = token_ids.shape
+        # Calculate the positions to sample from.
+        start_indices = torch.arange(
+            batch_size, dtype=torch.int32, device=input_lens.device) * seq_len
+        logits_indices = start_indices + input_lens - 1
+        attn_metadata = get_forward_context().attn_metadata
+
+        # FIXME(woosuk): This is a temporary hack to avoid using the existing
+        # sampler and sampling metadata.
+        sampling_metadata = SamplingMetadata(
+            seq_groups=[],
+            selected_token_indices=logits_indices,
+            categorized_sample_indices={},
+            num_prompts=attn_metadata.num_prefills,
+        )
+
+        # Skip this in memory profiling at initialization.
+        if kv_caches[0][0].numel() > 0:
+            # index_copy_(slot_mapping) only works when the inserted dimension
+            # is 0. However, the KV cache in the Pallas backend has the shape
+            # [num_kv_heads, num_blocks, block_size, head_size]. To make it
+            # work, we need to flatten the first three dimensions and modify
+            # the slot_mapping accordingly.
+            num_kv_heads, num_blocks, block_size, _ = kv_caches[0][0].shape
+            slot_mapping = attn_metadata.slot_mapping
+            slot_mapping = slot_mapping.flatten()
+            head_indices = torch.arange(0,
+                                        num_kv_heads,
+                                        device=slot_mapping.device,
+                                        dtype=slot_mapping.dtype)
+            head_indices *= block_size * num_blocks
+            slot_mapping = slot_mapping.repeat_interleave(num_kv_heads).view(
+                -1, num_kv_heads)
+            slot_mapping = slot_mapping + head_indices.view(1, -1)
+            slot_mapping = slot_mapping.flatten()
+            attn_metadata.slot_mapping = slot_mapping
+
+        hidden_states = self.model(token_ids, position_ids)
+        hidden_states = hidden_states.flatten(0, 1)
+        logits = self.model.compute_logits(hidden_states, sampling_metadata)
+
+        # Argmax sampling.
+        argmax_token_ids = torch.argmax(logits, dim=-1, keepdim=True)
+        argmax_token_ids = argmax_token_ids.repeat(1, num_samples)
+
+        # Zero temperature means greedy decoding. Avoid division by zero.
+        nonzero_t = torch.where(t != 0, t, 1.0)
+        logits = logits / nonzero_t.unsqueeze(dim=1)
+        if _ENABLE_TOP_P:
+            logits = _apply_top_p(logits, p.unsqueeze(dim=1))
+
+        # Random sampling.
+        probs = torch.softmax(logits, dim=-1, dtype=torch.float32)
+        sampled_token_ids = torch.multinomial(probs,
+                                              num_samples,
+                                              replacement=True)
+        if num_samples == 1:
+            argmax_token_ids = argmax_token_ids.squeeze(dim=-1)
+            sampled_token_ids = sampled_token_ids.squeeze(dim=-1)
+        next_token_ids = torch.where(t != 0, sampled_token_ids,
+                                     argmax_token_ids)
+        return next_token_ids
+
+
+def _get_padded_prefill_len(x: int) -> int:
+    # NOTE(woosuk): The pallas FlashAttention kernel requires the sequence
+    # length to be a multiple of 16. We pad the prompt length to the nearest
+    # multiple of 16. This is also good for performance.
+    if x <= 16:
+        return 16
+    return 1 << (x - 1).bit_length()
+
+
+def _get_padded_batch_size(batch_size: int) -> int:
+    # The GMM Pallas kernel requires num_tokens * topk to be a multiple of 16.
+    # To meet this requirement in the simplest way, we set the minimal batch
+    # size to 8.
+    if batch_size <= 8:
+        return 8
+    else:
+        return ((batch_size + 15) // 16) * 16
+
+
+def _apply_top_p(logits: torch.Tensor, p: torch.Tensor) -> torch.Tensor:
+    logits_sorted = torch.sort(logits, dim=-1, descending=True).values
+    sorted_cum_probs = torch.cumsum(logits_sorted.softmax(dim=-1), dim=-1)
+    cutoff_index = torch.sum(sorted_cum_probs < p, dim=-1, keepdim=True)
+    cutoff_logit = torch.gather(logits_sorted, -1, cutoff_index)
+    logits = logits.masked_fill_(logits < cutoff_logit, -float("inf"))
+    return logits
+
+
+def _make_decode_output(
+    next_token_ids: List[int],
+    seq_groups: List[List[int]],
+) -> SamplerOutput:
+    zero_logprob = Logprob(0.0)
+    sampler_outputs = []
+    batch_idx = 0
+    for seq_group in seq_groups:
+        seq_ids = seq_group
+        seq_outputs = []
+        for seq_id in seq_ids:
+            next_token_id = next_token_ids[batch_idx]
+            seq_outputs.append(
+                SequenceOutput(seq_id, next_token_id,
+                               {next_token_id: zero_logprob}))
+            batch_idx += 1
+        sampler_outputs.append(CompletionSequenceGroupOutput(
+            seq_outputs, None))
+    return SamplerOutput(sampler_outputs)

vllm/worker/tpu_worker.py

@@ -0,0 +1,337 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import os
+from typing import List, Optional, Tuple, Union
+
+import torch
+import torch_xla.core.xla_model as xm
+import torch_xla.debug.profiler as xp
+import torch_xla.runtime as xr
+
+import vllm.envs as envs
+from vllm.config import VllmConfig
+from vllm.distributed import (ensure_model_parallel_initialized,
+                              init_distributed_environment)
+from vllm.logger import init_logger
+from vllm.model_executor import set_random_seed
+from vllm.sequence import ExecuteModelRequest
+from vllm.utils import STR_DTYPE_TO_TORCH_DTYPE, bind_kv_cache, get_dtype_size
+from vllm.worker.tpu_model_runner import ExecutionMode, TPUModelRunner
+from vllm.worker.worker_base import (LocalOrDistributedWorkerBase,
+                                     LoRANotSupportedWorkerBase, WorkerBase,
+                                     WorkerInput)
+
+logger = init_logger(__name__)
+
+
+class TPUWorker(LoRANotSupportedWorkerBase, LocalOrDistributedWorkerBase):
+
+    def __init__(
+        self,
+        vllm_config: VllmConfig,
+        local_rank: int,
+        rank: int,
+        distributed_init_method: str,
+        is_driver_worker: bool,
+    ) -> None:
+        WorkerBase.__init__(self, vllm_config=vllm_config)
+        self.parallel_config.rank = rank
+        self.local_rank = local_rank
+        self.rank = rank
+        self.distributed_init_method = distributed_init_method
+        self.is_driver_worker = is_driver_worker
+
+        assert self.device_config.device_type == "tpu"
+        if self.cache_config.cache_dtype == "auto":
+            self.cache_dtype = self.model_config.dtype
+        else:
+            self.cache_dtype = STR_DTYPE_TO_TORCH_DTYPE[
+                self.cache_config.cache_dtype]
+
+        self.model_runner: TPUModelRunner = TPUModelRunner(
+            vllm_config=vllm_config, is_driver_worker=is_driver_worker)
+
+        if self.model_config.seed is None:
+            self.model_config.seed = 0
+
+        if vllm_config.lora_config is not None:
+            raise NotImplementedError(
+                "The V0 TPU backend doesn't support LoRA serving")
+
+    def init_device(self) -> None:
+        os.environ["PJRT_DEVICE"] = "TPU"
+        torch.set_grad_enabled(False)
+        torch.set_default_dtype(self.model_config.dtype)
+
+        # NOTE(woosuk): This is just to initialize the TP group and broadcast
+        # the input objects on CPU. The all-reduce and all-gather ops on TPU
+        # are invoked by `xm.all_reduce` and `xm.all_gather` which use their
+        # own context.
+        init_distributed_environment(
+            world_size=self.parallel_config.world_size,
+            rank=self.rank,
+            local_rank=self.local_rank,
+            distributed_init_method=self.distributed_init_method,
+            backend="gloo",
+        )
+        ensure_model_parallel_initialized(
+            self.parallel_config.tensor_parallel_size,
+            self.parallel_config.pipeline_parallel_size)
+
+        # Device initialization should happen after initializing the distributed
+        # runtime.
+        self.device = xm.xla_device()
+        self.device_config.device = self.device
+
+        # Set random seed.
+        set_random_seed(self.model_config.seed)
+        xm.set_rng_state(self.model_config.seed, self.device)
+
+        # Increase the cache size limit, which is the maximum number of
+        # dynamo graphs that can be compiled.
+        # NOTE(woosuk): Usually, we compile 10-15 graphs for prefill and
+        # 30-40 graphs for decode. 128 is an arbitrary safe number.
+        torch._dynamo.config.cache_size_limit = 128
+        # Use persistent cache to avoid XLA recompilation.
+        # NOTE(woosuk): Set per-rank cache path since different ranks
+        # can have slightly different XLA graphs.
+        world_size = self.parallel_config.world_size
+        rank = xr.global_ordinal()
+        # The PyTorch/XLA compilation cache uses the Torch IR to generate keys.
+        # Consequently, changes in optimization flags, which affect compilation
+        # results, don't change the cache key. This can result in the wrong
+        # compilation being used. To prevent this, disabling the XLA compilation
+        # cache during development is recommended.We can disable it by
+        # `export VLLM_XLA_CACHE_PATH=`
+        if envs.VLLM_XLA_CACHE_PATH:
+            per_rank_path = os.path.join(envs.VLLM_XLA_CACHE_PATH,
+                                         f"tp{world_size}_rank{rank}")
+            xr.initialize_cache(per_rank_path, readonly=False)
+
+        self.profiler = None
+        if envs.VLLM_TORCH_PROFILER_DIR and self.rank < 1:
+            # For TPU, we can only have 1 active profiler session for 1 profiler
+            # server. So we only profile on rank0.
+            self.profile_dir = envs.VLLM_TORCH_PROFILER_DIR
+            logger.info("Profiling enabled. Traces will be saved to: %s",
+                        self.profile_dir)
+            self.profiler = xp.start_server(9012)
+
+    def start_profile(self):
+        if self.rank < 1:
+            if self.profiler is None:
+                raise RuntimeError("Profiler is not enabled.")
+            xp.start_trace(self.profile_dir)
+
+    def stop_profile(self):
+        if self.rank < 1:
+            if self.profiler is None:
+                raise RuntimeError("Profiler is not enabled.")
+            xp.stop_trace()
+
+    def load_model(self):
+        self.model_runner.load_model()
+
+    def determine_num_available_blocks(self) -> Tuple[int, int]:
+        num_layers = self.model_config.get_num_layers(self.parallel_config)
+        head_size = self.model_config.get_head_size()
+        num_kv_heads = self.model_config.get_num_kv_heads(self.parallel_config)
+
+        # use an empty tensor instead of `None`` to force Dynamo to pass
+        # it by reference, rather by specializing on the value ``None``.
+        # the `dtype` argument does not matter, and we use `float32` as
+        # a placeholder (it has wide hardware support).
+        kv_caches = [(torch.tensor([], dtype=torch.float32,
+                                   device=self.device),
+                      torch.tensor([], dtype=torch.float32,
+                                   device=self.device))
+                     for _ in range(num_layers)]
+        bind_kv_cache(self.compilation_config.static_forward_context,
+                      [kv_caches])
+        self.model_runner._dummy_run(
+            batch_size=1,
+            seq_len=self.scheduler_config.max_num_batched_tokens,
+            kv_caches=kv_caches,
+            exec_mode=ExecutionMode.PREFILL,
+        )
+        # Synchronize before measuring the memory usage.
+        xm.wait_device_ops()
+
+        # Get the maximum amount of memory used by the model weights and
+        # intermediate activations.
+        m = xm.get_memory_info(self.device)
+        total_memory_size = m["bytes_limit"]
+        profiled = m["peak_bytes_used"]  # Weights + intermediate activations.
+
+        # Calculate the TPU KV cache size based on profiling.
+        usable_memory_size = int(total_memory_size *
+                                 self.cache_config.gpu_memory_utilization)
+        tpu_kv_cache_bytes = max(usable_memory_size - profiled, 0)
+        dtype_bytes = get_dtype_size(self.cache_dtype)
+        block_size_bytes = (dtype_bytes * self.cache_config.block_size *
+                            num_layers * 2 * head_size * num_kv_heads)
+        num_tpu_blocks = tpu_kv_cache_bytes // block_size_bytes
+        num_tpu_blocks = (num_tpu_blocks // 8) * 8  # Round down to 8.
+
+        # Calculate the CPU KV cache size based on the config.
+        num_cpu_blocks = int(self.cache_config.swap_space_bytes //
+                             block_size_bytes)
+        num_cpu_blocks = (num_cpu_blocks // 8) * 8  # Round down to 8.
+        return num_tpu_blocks, num_cpu_blocks
+
+    def initialize_cache(
+        self,
+        num_gpu_blocks: int,
+        num_cpu_blocks: int,
+    ) -> None:
+        self.cache_config.num_gpu_blocks = num_gpu_blocks
+        self.cache_config.num_cpu_blocks = num_cpu_blocks
+        self.block_size = self.cache_config.block_size
+
+        dtype = self.cache_dtype
+        num_layers = self.model_config.get_num_layers(self.parallel_config)
+        num_kv_heads = self.model_config.get_num_kv_heads(self.parallel_config)
+        head_size = self.model_config.get_head_size()
+
+        self.cpu_cache: List[Tuple[torch.Tensor, torch.Tensor]] = []
+        self.tpu_cache: List[Tuple[torch.Tensor, torch.Tensor]] = []
+        tpu_cache_shape = self.model_runner.attn_backend.get_kv_cache_shape(
+            num_gpu_blocks, self.block_size, num_kv_heads, head_size)
+        cpu_cache_shape = self.model_runner.attn_backend.get_kv_cache_shape(
+            num_cpu_blocks, self.block_size, num_kv_heads, head_size)
+        for _ in range(num_layers):
+            tpu_k_cache = torch.zeros(tpu_cache_shape,
+                                      dtype=dtype,
+                                      device=self.device)
+            tpu_v_cache = torch.zeros_like(tpu_k_cache)
+            self.tpu_cache.append((tpu_k_cache, tpu_v_cache))
+            cpu_k_cache = torch.zeros(cpu_cache_shape,
+                                      dtype=dtype,
+                                      device="cpu")
+            cpu_v_cache = torch.zeros_like(cpu_k_cache)
+            self.cpu_cache.append((cpu_k_cache, cpu_v_cache))
+        bind_kv_cache(self.compilation_config.static_forward_context,
+                      [self.tpu_cache])
+        self._warmup_model()
+
+    def _warmup_model(self) -> None:
+        # FIXME(woosuk): Here we are abusing `enforce_eager` which is defined
+        # for CUDA graphs. We should refactor this part.
+        if not self.model_config.enforce_eager:
+            # Warm up the model with all possible input shapes so that
+            # compilation never happens during the actual execution.
+            # This may take ~30 mins for the first run and ~20 mins for the
+            # subsequent runs.
+            # If `enforce_eager` is True, the ahead-of-time compilation is
+            # skipped and the compilation happens during the actual execution,
+            # which is bad for performance but useful for development.
+            self.model_runner.warmup_model(self.tpu_cache)
+
+    def get_cache_block_size_bytes(self) -> int:
+        head_size = self.model_config.get_head_size()
+        num_heads = self.model_config.get_num_kv_heads(self.parallel_config)
+        num_layers = self.model_config.get_num_layers(self.parallel_config)
+
+        key_cache_block = self.cache_config.block_size * num_heads * head_size
+        value_cache_block = key_cache_block
+        total = num_layers * (key_cache_block + value_cache_block)
+        dtype_size = get_dtype_size(self.cache_dtype)
+        return dtype_size * total
+
+    @property
+    def do_metadata_broadcast(self) -> bool:
+        return self.parallel_config.tensor_parallel_size > 1
+
+    @property
+    def kv_cache(self) -> Optional[List[List[torch.Tensor]]]:
+        # NOTE(woosuk): This assumes virtual_engine == 0, i.e., no pipeline
+        # parallelism.
+        return [self.tpu_cache]
+
+    def prepare_worker_input(
+        self,
+        execute_model_req: ExecuteModelRequest,
+    ) -> WorkerInput:
+        virtual_engine = execute_model_req.virtual_engine
+        num_seq_groups = len(execute_model_req.seq_group_metadata_list)
+        blocks_to_swap_in = _make_src_to_dst(
+            execute_model_req.blocks_to_swap_in, "cpu", self.device)
+        blocks_to_swap_out = _make_src_to_dst(
+            execute_model_req.blocks_to_swap_out, self.device, "cpu")
+        blocks_to_copy = _make_src_to_dst(execute_model_req.blocks_to_copy,
+                                          self.device, self.device)
+        return WorkerInput(
+            num_seq_groups=num_seq_groups,
+            blocks_to_swap_in=blocks_to_swap_in,
+            blocks_to_swap_out=blocks_to_swap_out,
+            blocks_to_copy=blocks_to_copy,
+            virtual_engine=virtual_engine,
+        )
+
+    def execute_worker(self, worker_input: WorkerInput) -> None:
+        virtual_engine = worker_input.virtual_engine
+        assert virtual_engine == 0
+        attn_backend = self.model_runner.attn_backend
+        num_layers = self.model_config.get_num_layers(self.parallel_config)
+
+        # Issue cache operations.
+        if worker_input.blocks_to_swap_in is not None:
+            src_indices, dst_indices = worker_input.blocks_to_swap_in
+            if src_indices.numel() > 0:
+                # Swap from CPU to TPU.
+                for i in range(num_layers):
+                    tpu_k_cache, tpu_v_cache = self.tpu_cache[i]
+                    cpu_k_cache, cpu_v_cache = self.cpu_cache[i]
+                    k = cpu_k_cache[:, src_indices].to(self.device)
+                    v = cpu_v_cache[:, src_indices].to(self.device)
+                    _insert_kv(k, v, dst_indices, tpu_k_cache, tpu_v_cache)
+
+        if worker_input.blocks_to_swap_out is not None:
+            src_indices, dst_indices = worker_input.blocks_to_swap_out
+            if src_indices.numel() > 0:
+                # Swap from TPU to CPU.
+                for i in range(num_layers):
+                    tpu_k_cache, tpu_v_cache = self.tpu_cache[i]
+                    cpu_k_cache, cpu_v_cache = self.cpu_cache[i]
+                    cpu_k_cache[:, dst_indices] = tpu_k_cache[:, src_indices]
+                    cpu_v_cache[:, dst_indices] = tpu_v_cache[:, src_indices]
+
+        if worker_input.blocks_to_copy is not None:
+            src_indices, dst_indices = worker_input.blocks_to_copy
+            if src_indices.numel() > 0:
+                attn_backend.copy_blocks(self.tpu_cache,
+                                         (src_indices, dst_indices))
+
+
+def _make_src_to_dst(
+    mapping: List[Tuple[int, int]],
+    src_device: Union[torch.device, str],
+    dst_device: Union[torch.device, str],
+) -> Optional[Tuple[torch.Tensor, torch.Tensor]]:
+    if not mapping:
+        return None
+
+    src_indices = [i for i, _ in mapping]
+    dst_indices = [i for _, i in mapping]
+    src_indices = torch.tensor(src_indices,
+                               device=src_device,
+                               dtype=torch.int64)
+    dst_indices = torch.tensor(dst_indices,
+                               device=dst_device,
+                               dtype=torch.int64)
+    return src_indices, dst_indices
+
+
+@torch.compile(backend="openxla")
+def _insert_kv(
+    k: torch.Tensor,
+    v: torch.Tensor,
+    indices: torch.Tensor,
+    tpu_k_cache: torch.Tensor,
+    tpu_v_cache: torch.Tensor,
+) -> None:
+    torch.ops.xla.dynamo_set_buffer_donor_(tpu_k_cache, True)
+    torch.ops.xla.dynamo_set_buffer_donor_(tpu_v_cache, True)
+    tpu_k_cache[:, indices] = k
+    tpu_v_cache[:, indices] = v

vllm/worker/xpu_model_runner.py

@@ -0,0 +1,606 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import dataclasses
+import time
+import weakref
+from collections import defaultdict
+from dataclasses import dataclass
+from typing import (TYPE_CHECKING, Any, Callable, Dict, List, Optional, Tuple,
+                    Type, TypeVar)
+
+import torch
+import torch.nn as nn
+
+from vllm.attention import get_attn_backend
+from vllm.config import VllmConfig
+from vllm.distributed import get_pp_group
+from vllm.forward_context import set_forward_context
+from vllm.inputs import INPUT_REGISTRY, InputRegistry
+from vllm.logger import init_logger
+from vllm.model_executor import SamplingMetadataCache
+from vllm.model_executor.layers.sampler import SamplerOutput, get_sampler
+from vllm.model_executor.model_loader import get_model
+from vllm.multimodal import (MULTIMODAL_REGISTRY, BatchedTensorInputs,
+                             MultiModalKwargs, MultiModalPlaceholderMap,
+                             MultiModalRegistry)
+from vllm.sampling_params import SamplingParams
+from vllm.sequence import IntermediateTensors, SequenceGroupMetadata
+from vllm.utils import DeviceMemoryProfiler, GiB_bytes, make_tensor_with_pad
+from vllm.worker.model_runner import AttentionMetadata, SamplingMetadata
+from vllm.worker.model_runner_base import (
+    ModelRunnerBase, ModelRunnerInputBase, ModelRunnerInputBuilderBase,
+    _add_attn_metadata_broadcastable_dict,
+    _add_sampling_metadata_broadcastable_dict,
+    _init_attn_metadata_from_tensor_dict,
+    _init_sampling_metadata_from_tensor_dict)
+
+if TYPE_CHECKING:
+    from vllm.attention.backends.abstract import AttentionBackend
+
+logger = init_logger(__name__)
+
+_PAD_SLOT_ID = -1
+
+TModelInputForXPU = TypeVar('TModelInputForXPU', bound="ModelInputForXPU")
+
+
+@dataclass(frozen=True)
+class ModelInputForXPU(ModelRunnerInputBase):
+    """
+    Used by the NeuronModelRunner.
+    """
+    input_tokens: Optional[torch.Tensor] = None
+    input_positions: Optional[torch.Tensor] = None
+    attn_metadata: Optional["AttentionMetadata"] = None
+    multi_modal_kwargs: Optional[BatchedTensorInputs] = None
+    virtual_engine: Optional[int] = None
+    seq_lens: Optional[List[int]] = None
+    query_lens: Optional[List[int]] = None
+    async_callback: Optional[Callable] = None
+
+    def as_broadcastable_tensor_dict(self) -> Dict[str, Any]:
+        tensor_dict = {
+            "input_tokens": self.input_tokens,
+            "input_positions": self.input_positions,
+        }
+        _add_attn_metadata_broadcastable_dict(tensor_dict, self.attn_metadata)
+
+        return tensor_dict
+
+    @classmethod
+    def from_broadcasted_tensor_dict(
+        cls: Type[TModelInputForXPU],
+        tensor_dict: Dict[str, Any],
+        attn_backend: Optional["AttentionBackend"] = None,
+    ) -> TModelInputForXPU:
+        if attn_backend is not None:
+            tensor_dict = _init_attn_metadata_from_tensor_dict(
+                attn_backend, tensor_dict)
+        return cls(**tensor_dict)
+
+
+@dataclass(frozen=True)
+class ModelInputForXPUWithSamplingMetadata(ModelInputForXPU):
+    """
+    Used by the ModelRunner.
+    """
+    sampling_metadata: Optional["SamplingMetadata"] = None
+
+    def as_broadcastable_tensor_dict(self) -> Dict[str, Any]:
+        tensor_dict = {
+            "input_tokens": self.input_tokens,
+            "input_positions": self.input_positions,
+        }
+        _add_attn_metadata_broadcastable_dict(tensor_dict, self.attn_metadata)
+        _add_sampling_metadata_broadcastable_dict(tensor_dict,
+                                                  self.sampling_metadata)
+        return tensor_dict
+
+    @classmethod
+    def from_broadcasted_tensor_dict(
+        cls,
+        tensor_dict: Dict[str, Any],
+        attn_backend: Optional["AttentionBackend"] = None,
+    ) -> "ModelInputForXPUWithSamplingMetadata":
+        tensor_dict = _init_sampling_metadata_from_tensor_dict(tensor_dict)
+        if attn_backend is not None:
+            tensor_dict = _init_attn_metadata_from_tensor_dict(
+                attn_backend, tensor_dict)
+        return cls(**tensor_dict)
+
+
+class ModelInputForXPUBuilder(ModelRunnerInputBuilderBase[ModelInputForXPU]):
+
+    def __init__(self,
+                 runner: "XPUModelRunner",
+                 finished_requests_ids: Optional[List[str]] = None) -> None:
+        super().__init__()
+        self.runner = runner
+        self.model_input_cls = self.runner._model_input_cls
+        self.attn_backend = self.runner.attn_backend
+        self.sliding_window = self.runner.sliding_window
+        self.block_size = self.runner.block_size
+        self.device = self.runner.device
+
+    def prepare(self,
+                finished_requests_ids: Optional[List[str]] = None) -> None:
+        self.seq_group_metadata_list: List[SequenceGroupMetadata] = []
+
+    def add_seq_group(self, seq_group_metadata: SequenceGroupMetadata):
+        self.seq_group_metadata_list.append(seq_group_metadata)
+
+    def build(self) -> ModelInputForXPU:
+        is_prompt = self.seq_group_metadata_list[0].is_prompt
+        # Prepare input tensors.
+        if is_prompt:
+            (input_tokens, input_positions, attn_metadata, seq_lens,
+             multi_modal_kwargs) = self._prepare_prompt(
+                 self.seq_group_metadata_list)
+        else:
+            (input_tokens, input_positions,
+             attn_metadata) = self._prepare_decode(
+                 self.seq_group_metadata_list)
+            seq_lens = None
+            multi_modal_kwargs = None
+
+        return self.model_input_cls(
+            input_tokens=input_tokens,
+            input_positions=input_positions,
+            attn_metadata=attn_metadata,
+            multi_modal_kwargs=multi_modal_kwargs,
+            seq_lens=seq_lens,
+            query_lens=seq_lens,
+        )
+
+    def _prepare_prompt(
+        self,
+        seq_group_metadata_list: List[SequenceGroupMetadata],
+    ) -> Tuple[torch.Tensor, torch.Tensor, AttentionMetadata, List[int],
+               BatchedTensorInputs]:
+        assert len(seq_group_metadata_list) > 0
+        input_tokens: List[int] = []
+        input_positions: List[int] = []
+        slot_mapping: List[int] = []
+        seq_lens: List[int] = []
+        multi_modal_kwargs_list: List[MultiModalKwargs] = []
+        multi_modal_placeholder_maps: Dict[
+            str,
+            MultiModalPlaceholderMap] = defaultdict(MultiModalPlaceholderMap)
+
+        for seq_group_metadata in seq_group_metadata_list:
+            assert seq_group_metadata.is_prompt
+            seq_ids = list(seq_group_metadata.seq_data.keys())
+            assert len(seq_ids) == 1
+            seq_id = seq_ids[0]
+
+            seq_data = seq_group_metadata.seq_data[seq_id]
+            prompt_tokens = seq_data.get_token_ids()
+            computed_len = seq_data.get_num_computed_tokens()
+            seq_len = len(prompt_tokens)
+
+            seq_lens.append(seq_len)  # Prompt token num
+            input_tokens.extend(prompt_tokens)  # Token ids
+
+            # Token position ids
+            # NOTE(woosuk): Here we assume that the first token in the prompt
+            # is always the first token in the sequence.
+            positions_range = range(computed_len, seq_len)
+            input_positions.extend(list(positions_range))
+
+            if seq_group_metadata.multi_modal_data:
+                # NOTE: mm_kwargs only includes the subset of multi-modal items
+                # that intersect with the current prefill positions.
+                mm_kwargs, placeholder_maps = MultiModalPlaceholderMap \
+                    .from_seq_group(seq_group_metadata, positions_range)
+
+                multi_modal_kwargs_list.append(mm_kwargs)
+
+                for modality, placeholder_map in placeholder_maps.items():
+                    multi_modal_placeholder_maps[modality].extend(
+                        placeholder_map)
+
+            if seq_group_metadata.block_tables is None:
+                # During memory profiling, the block tables are not initialized
+                # yet. In this case, we just use a dummy slot mapping.
+                slot_mapping.extend([_PAD_SLOT_ID] * seq_len)
+                continue
+
+            # Compute the slot mapping.
+            block_table = seq_group_metadata.block_tables[seq_id]
+            # Mask the [0, start_idx) tokens of the prompt with _PAD_SLOT_ID,
+            # where start_idx is max(0, seq_len - sliding_window).
+            # For example, if the prompt len is 10, sliding window is 8, and
+            # block size is 4, the first two tokens are masked and the slot
+            # mapping will be [-1, -1, 2, 3, 4, 5, 6, 7, 0, 1].
+            start_idx = 0
+            if self.sliding_window is not None:
+                start_idx = max(0, seq_len - self.sliding_window)
+
+            for i in range(computed_len, seq_len):
+                if i < start_idx:
+                    slot_mapping.append(_PAD_SLOT_ID)
+                    continue
+
+                block_number = block_table[i //
+                                           self.block_size]  # type: ignore
+                block_offset = i % self.block_size  # type: ignore
+                slot = block_number * self.block_size + block_offset
+                slot_mapping.append(slot)
+
+        num_prompt_tokens = len(input_tokens)
+
+        input_tokens = torch.tensor(input_tokens,
+                                    dtype=torch.long,
+                                    device=self.device)  # type: ignore
+        input_positions = torch.tensor(input_positions,
+                                       dtype=torch.long,
+                                       device=self.device)  # type: ignore
+        slot_mapping = torch.tensor(slot_mapping,
+                                    dtype=torch.long,
+                                    device=self.device)  # type: ignore
+        placeholder_index_maps = {
+            modality: placeholder_map.index_map()
+            for modality, placeholder_map in
+            multi_modal_placeholder_maps.items()
+        }
+
+        max_seqlen = max(seq_lens)
+        tmp = [0]
+        tmp.extend(seq_lens)
+        seqlen = torch.tensor(tmp)
+        seqlen_q = torch.cumsum(seqlen, dim=0).to(device=self.device)
+
+        attn_metadata = self.attn_backend.make_metadata(
+            is_prompt=True,
+            slot_mapping=slot_mapping,
+            multi_modal_placeholder_index_maps=placeholder_index_maps,
+            enable_kv_scales_calculation=False,
+            seq_lens=seq_lens,
+            seqlen_q=seqlen_q,
+            max_seqlen=max_seqlen,
+            seq_lens_tensor=torch.tensor([]),
+            max_decode_seq_len=0,
+            num_prefills=len(seq_lens),
+            num_prefill_tokens=num_prompt_tokens,
+            num_decode_tokens=0,
+            block_tables=torch.tensor([], device=self.device, dtype=torch.int),
+        )
+
+        multi_modal_kwargs = MultiModalKwargs.batch(multi_modal_kwargs_list)
+
+        return (input_tokens, input_positions, attn_metadata, seq_lens,
+                multi_modal_kwargs)
+
+    def _prepare_decode(
+        self,
+        seq_group_metadata_list: List[SequenceGroupMetadata],
+    ) -> Tuple[torch.Tensor, torch.Tensor, AttentionMetadata]:
+        assert len(seq_group_metadata_list) > 0
+        input_tokens: List[int] = []
+        input_positions: List[int] = []
+        slot_mapping: List[int] = []
+        seq_lens: List[int] = []
+        block_tables: List[List[int]] = []
+
+        for seq_group_metadata in seq_group_metadata_list:
+            assert not seq_group_metadata.is_prompt
+            assert seq_group_metadata.token_chunk_size == 1
+
+            seq_ids = list(seq_group_metadata.seq_data.keys())
+
+            for seq_id in seq_ids:
+                seq_data = seq_group_metadata.seq_data[seq_id]
+                generation_token = seq_data.get_last_token_id()
+                input_tokens.append(generation_token)
+
+                seq_len = seq_data.get_len()
+                position = seq_len - 1
+                input_positions.append(position)
+
+                seq_len = seq_len if self.sliding_window is None else min(
+                    seq_len, self.sliding_window)
+                seq_lens.append(seq_len)
+
+                block_table = seq_group_metadata.block_tables[seq_id]
+                block_number = block_table[position // self.block_size]
+                block_offset = position % self.block_size
+                slot = block_number * self.block_size + block_offset
+                slot_mapping.append(slot)
+
+                if self.sliding_window is not None:
+                    sliding_window_blocks = (self.sliding_window //
+                                             self.block_size)
+                    block_table = block_table[-sliding_window_blocks:]
+                block_tables.append(block_table)
+
+        max_decode_seq_len = max(seq_lens)
+
+        input_tokens = torch.tensor(input_tokens,
+                                    dtype=torch.long,
+                                    device=self.device)
+        input_positions = torch.tensor(input_positions,
+                                       dtype=torch.long,
+                                       device=self.device)
+        slot_mapping = torch.tensor(slot_mapping,
+                                    dtype=torch.long,
+                                    device=self.device)
+        seq_lens_tensor = torch.tensor(seq_lens,
+                                       dtype=torch.int,
+                                       device=self.device)
+
+        block_tables = make_tensor_with_pad(
+            block_tables,
+            pad=0,
+            dtype=torch.int,
+            device=self.device,
+        )
+
+        attn_metadata = self.attn_backend.make_metadata(
+            is_prompt=False,
+            slot_mapping=slot_mapping,
+            multi_modal_placeholder_index_maps=None,
+            enable_kv_scales_calculation=False,
+            seq_lens=seq_lens,
+            seqlen_q=torch.tensor([]),
+            max_seqlen=0,
+            seq_lens_tensor=seq_lens_tensor,
+            max_decode_seq_len=max_decode_seq_len,
+            num_prefill_tokens=0,
+            num_decode_tokens=len(input_tokens),
+            num_prefills=0,
+            block_tables=block_tables,
+        )
+        return (
+            input_tokens,
+            input_positions,
+            attn_metadata,
+        )
+
+
+class XPUModelRunner(ModelRunnerBase[ModelInputForXPUWithSamplingMetadata]):
+    _model_input_cls: Type[ModelInputForXPUWithSamplingMetadata] = (
+        ModelInputForXPUWithSamplingMetadata)
+    _builder_cls: Type[ModelInputForXPUBuilder] = ModelInputForXPUBuilder
+
+    def __init__(
+        self,
+        vllm_config: VllmConfig,
+        kv_cache_dtype: Optional[str] = "auto",
+        is_driver_worker: bool = False,
+        return_hidden_states: bool = False,
+        input_registry: InputRegistry = INPUT_REGISTRY,
+        mm_registry: MultiModalRegistry = MULTIMODAL_REGISTRY,
+    ):
+
+        ModelRunnerBase.__init__(self, vllm_config=vllm_config)
+        model_config = self.model_config
+        cache_config = self.cache_config
+        self.is_driver_worker = is_driver_worker
+        self.return_hidden_states = return_hidden_states
+
+        self.device = self.device_config.device
+
+        self.kv_cache_dtype = kv_cache_dtype
+        self.sliding_window = model_config.get_sliding_window()
+        self.block_size = cache_config.block_size
+
+        self.attn_backend = get_attn_backend(
+            self.model_config.get_head_size(),
+            self.model_config.dtype,
+            self.kv_cache_dtype,
+            self.block_size,
+            self.model_config.is_attention_free,
+        )
+
+        # Multi-modal data support
+        self.input_registry = input_registry
+        self.mm_registry = mm_registry
+
+        # Lazy initialization.
+        self.model: nn.Module  # Set after init_Model
+        self.sampler = get_sampler()
+
+        self.sampling_metadata_cache: SamplingMetadataCache = \
+              SamplingMetadataCache() \
+                if self.parallel_config.pipeline_parallel_size == 1 else None
+
+        self.builder = self._builder_cls(weakref.proxy(self))
+
+    def load_model(self) -> None:
+        with DeviceMemoryProfiler() as m:
+            self.model = get_model(vllm_config=self.vllm_config)
+
+        self.model_memory_usage = m.consumed_memory
+        logger.info("Loading model weights took %.4f GiB",
+                    self.model_memory_usage / GiB_bytes)
+
+    def get_model(self) -> nn.Module:
+        return self.model
+
+    @property
+    def vocab_size(self) -> int:
+        return self.model_config.get_vocab_size()
+
+    @torch.inference_mode()
+    def profile_run(self) -> None:
+        # Enable top-k sampling to reflect the accurate memory usage.
+        sampling_params = SamplingParams(top_p=0.99, top_k=self.vocab_size - 1)
+        max_num_batched_tokens = self.scheduler_config.max_num_batched_tokens
+        max_num_seqs = self.scheduler_config.max_num_seqs
+
+        # Profile memory usage with max_num_sequences sequences and the total
+        # number of tokens equal to max_num_batched_tokens.
+        seqs: List[SequenceGroupMetadata] = []
+        # Additional GPU memory may be needed for multi-modal encoding, which
+        # needs to be accounted for when calculating the GPU blocks for
+        # vLLM blocker manager.
+        # To exercise the worst scenario for GPU memory consumption,
+        # the number of seqs (batch_size) is chosen to maximize the number
+        # of images processed.
+        max_mm_tokens = self.mm_registry.get_max_multimodal_tokens(
+            self.model_config)
+        if max_mm_tokens > 0:
+            max_num_seqs_orig = max_num_seqs
+            max_num_seqs = min(max_num_seqs,
+                               max_num_batched_tokens // max_mm_tokens)
+            if max_num_seqs < 1:
+                expr = (f"min({max_num_seqs_orig}, "
+                        f"{max_num_batched_tokens} // {max_mm_tokens})")
+                logger.warning(
+                    "Computed max_num_seqs (%s) to be less than 1. "
+                    "Setting it to the minimum value of 1.", expr)
+                max_num_seqs = 1
+
+        batch_size = 0
+        for group_id in range(max_num_seqs):
+            seq_len = (max_num_batched_tokens // max_num_seqs +
+                       (group_id < max_num_batched_tokens % max_num_seqs))
+            batch_size += seq_len
+
+            dummy_data = self.input_registry \
+                .dummy_data_for_profiling(self.model_config,
+                                          seq_len,
+                                          self.mm_registry)
+
+            seq = SequenceGroupMetadata(
+                request_id=str(group_id),
+                is_prompt=True,
+                seq_data={group_id: dummy_data.seq_data},
+                sampling_params=sampling_params,
+                block_tables=None,
+                lora_request=None,
+                multi_modal_data=dummy_data.multi_modal_data,
+                multi_modal_placeholders=dummy_data.multi_modal_placeholders)
+            seqs.append(seq)
+
+        finished_requests_ids = [seq.request_id for seq in seqs]
+        model_input = self.prepare_model_input(
+            seqs, finished_requests_ids=finished_requests_ids)
+        intermediate_tensors = None
+        if not get_pp_group().is_first_rank:
+            intermediate_tensors = self.model.make_empty_intermediate_tensors(
+                batch_size=batch_size,
+                dtype=self.model_config.dtype,
+                device=self.device)
+        self.execute_model(model_input, None, intermediate_tensors)
+        torch.xpu.synchronize()
+        return
+
+    def make_model_input_from_broadcasted_tensor_dict(
+            self,
+            tensor_dict: Dict[str,
+                              Any]) -> ModelInputForXPUWithSamplingMetadata:
+        return (
+            ModelInputForXPUWithSamplingMetadata.from_broadcasted_tensor_dict(
+                tensor_dict,
+                attn_backend=self.attn_backend,
+            ))
+
+    def _prepare_model_input_tensors(
+        self,
+        seq_group_metadata_list: List[SequenceGroupMetadata],
+        finished_requests_ids: Optional[List[str]] = None
+    ) -> ModelInputForXPUWithSamplingMetadata:
+        """Helper method to prepare the model input based on a given sequence
+        group. Prepares metadata needed for the base model forward pass but not
+        metadata for possible additional steps, e.g., sampling.
+
+        """
+        builder = self.builder
+        builder.prepare(finished_requests_ids)
+        for seq_group_metadata in seq_group_metadata_list:
+            builder.add_seq_group(seq_group_metadata)
+
+        return builder.build()  # type: ignore
+
+    def prepare_model_input(
+        self,
+        seq_group_metadata_list: List[SequenceGroupMetadata],
+        virtual_engine: int = 0,
+        finished_requests_ids: Optional[List[str]] = None
+    ) -> ModelInputForXPUWithSamplingMetadata:
+        """Prepare the model input based on a given sequence group, including
+        metadata for the sampling step.
+
+        """
+        model_input = self._prepare_model_input_tensors(
+            seq_group_metadata_list, finished_requests_ids)
+        # Sampling metadata is only required for the final pp group
+        generators = self.get_generators(finished_requests_ids)
+        sampling_metadata = SamplingMetadata.prepare(
+            seq_group_metadata_list,
+            model_input.seq_lens,
+            model_input.query_lens,
+            self.device,
+            pin_memory=False,
+            generators=generators,
+            cache=self.sampling_metadata_cache)
+
+        return dataclasses.replace(model_input,
+                                   sampling_metadata=sampling_metadata,
+                                   virtual_engine=virtual_engine)
+
+    @torch.inference_mode()
+    def execute_model(
+        self,
+        model_input: ModelInputForXPUWithSamplingMetadata,
+        kv_caches: List[torch.Tensor],
+        intermediate_tensors: Optional[IntermediateTensors] = None,
+        num_steps: int = 1,
+    ) -> Optional[List[SamplerOutput]]:
+        if num_steps > 1:
+            raise ValueError(
+                "XPUModelRunner does not support multi-step execution.")
+
+        model_executable = self.model
+        if (self.observability_config is not None
+                and self.observability_config.collect_model_forward_time):
+            model_forward_start_time = time.time()
+        with set_forward_context(model_input.attn_metadata, self.vllm_config,
+                                 model_input.virtual_engine):
+            hidden_or_intermediate_states = model_executable(
+                input_ids=model_input.input_tokens,
+                positions=model_input.input_positions,
+                intermediate_tensors=intermediate_tensors,
+                **MultiModalKwargs.as_kwargs(
+                    model_input.multi_modal_kwargs or {},
+                    device=self.device,
+                ),
+            )
+        # Compute the logits in the last pipeline stage.
+        if not get_pp_group().is_last_rank:
+            return hidden_or_intermediate_states
+
+        if (self.observability_config is not None
+                and self.observability_config.collect_model_forward_time):
+            model_forward_end_time = time.time()
+
+        # Compute the logits.
+        logits = self.model.compute_logits(hidden_or_intermediate_states,
+                                           model_input.sampling_metadata)
+
+        # Only perform sampling in the driver worker.
+        if not self.is_driver_worker:
+            return []
+
+        if model_input.async_callback is not None:
+            model_input.async_callback()
+
+        # Sample the next token.
+        output: SamplerOutput = self.sampler(
+            logits=logits,
+            sampling_metadata=model_input.sampling_metadata,
+        )
+        if (self.observability_config is not None
+                and self.observability_config.collect_model_forward_time
+                and output is not None):
+            model_forward_time = (model_forward_end_time -
+                                  model_forward_start_time)
+            # If there are multiple workers, we are still tracking the latency
+            # from the start time of the driver worker to the end time of the
+            # driver worker. The model forward time will then end up covering
+            # the communication time as well.
+            output.model_forward_time = model_forward_time
+
+        return [output]

vllm/worker/xpu_worker.py

@@ -0,0 +1,186 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""A XPU worker class."""
+import gc
+import os
+from typing import List, Optional, Tuple
+
+import intel_extension_for_pytorch  # noqa: F401
+import oneccl_bindings_for_pytorch  # noqa: F401
+import torch
+import torch.distributed
+
+from vllm.config import VllmConfig
+from vllm.distributed import (ensure_model_parallel_initialized,
+                              init_distributed_environment)
+from vllm.distributed.parallel_state import get_pp_group
+from vllm.logger import init_logger
+from vllm.model_executor import set_random_seed
+from vllm.platforms import current_platform
+from vllm.worker.cache_engine import CacheEngine
+from vllm.worker.worker import Worker
+from vllm.worker.worker_base import LoRANotSupportedWorkerBase, WorkerBase
+from vllm.worker.xpu_model_runner import XPUModelRunner
+
+logger = init_logger(__name__)
+
+
+class XPUWorker(LoRANotSupportedWorkerBase, Worker):
+    """A worker class that executes (a partition of) the model on a GPU.
+
+    Each worker is associated with a single XPU device. The worker is 
+    responsible for maintaining the KV cache and executing the model on the 
+    XPU. In case of distributed inference, each worker is assigned a partition
+    of the model.
+    """
+
+    def __init__(
+        self,
+        vllm_config: VllmConfig,
+        local_rank: int,
+        rank: int,
+        distributed_init_method: str,
+        is_driver_worker: bool = False,
+    ) -> None:
+        WorkerBase.__init__(self, vllm_config=vllm_config)
+        device_config = self.device_config
+        parallel_config = self.parallel_config
+        assert device_config.device_type == "xpu"
+        assert current_platform.is_xpu()
+
+        self.parallel_config.rank = rank
+
+        self.local_rank = local_rank
+        self.rank = rank
+        self.distributed_init_method = distributed_init_method
+        self.is_driver_worker = is_driver_worker
+        if parallel_config and is_driver_worker:
+            assert rank % parallel_config.tensor_parallel_size == 0, \
+                   "Driver worker should be rank 0 of tensor parallel group."
+
+        self.model_runner = XPUModelRunner(  # type: ignore
+            vllm_config=vllm_config,
+            kv_cache_dtype=self.cache_config.cache_dtype,
+            is_driver_worker=is_driver_worker,
+        )
+        # Uninitialized cache engine. Will be initialized by
+        # initialize_cache.
+        self.cache_engine: List[CacheEngine]
+        self.gpu_cache: Optional[List[List[torch.Tensor]]]
+
+    def init_device(self) -> None:
+        if self.device_config.device.type == "xpu" and current_platform.is_xpu(
+        ):
+            self.device = torch.device(f"xpu:{self.local_rank}")
+            torch.xpu.set_device(self.device)
+            torch.xpu.empty_cache()
+            self.init_gpu_memory = torch.xpu.get_device_properties(
+                self.local_rank).total_memory
+        else:
+            raise RuntimeError(
+                f"Not support device type: {self.device_config.device}")
+        # Initialize the distributed environment.
+        self.init_worker_distributed_environment()
+        # Initialize the model.
+        set_random_seed(self.model_config.seed)
+
+    # keep this method for `empty_cache` and `synchronize` api
+    @torch.inference_mode()
+    def determine_num_available_blocks(self) -> Tuple[int, int]:
+        """Profiles the peak memory usage of the model to determine how many
+        KV blocks may be allocated without OOMs.
+
+        The engine will first conduct a profiling of the existing memory usage.
+        Then, it calculate the maximum possible number of GPU and CPU blocks
+        that can be allocated with the remaining free memory.
+
+        Tip:
+            You may limit the usage of GPU memory
+            by adjusting the `gpu_memory_utilization` parameter.
+        """
+        # Profile the memory usage of the model and get the maximum number of
+        # cache blocks that can be allocated with the remaining free memory.
+        torch.xpu.empty_cache()
+
+        # Execute a forward pass with dummy inputs to profile the memory usage
+        # of the model.
+        self.model_runner.profile_run()
+
+        # Calculate the number of blocks that can be allocated with the
+        # profiled peak memory.
+        torch.xpu.synchronize()
+        used_memory = torch.xpu.memory_allocated()
+        total_gpu_memory = torch.xpu.get_device_properties(
+            self.local_rank).total_memory
+        free_gpu_memory = total_gpu_memory - used_memory
+
+        # NOTE(woosuk): Here we assume that the other processes using the same
+        # GPU did not change their memory usage during the profiling.
+        peak_memory = self.init_gpu_memory - free_gpu_memory
+        assert peak_memory > 0, (
+            "Error in memory profiling. "
+            f"Initial free memory {self.init_gpu_memory}, current free memory"
+            f" {free_gpu_memory}. This happens when the GPU memory was "
+            "not properly cleaned up before initializing the vLLM instance.")
+
+        cache_block_size = self.get_cache_block_size_bytes()
+        num_gpu_blocks = int(
+            (total_gpu_memory * self.cache_config.gpu_memory_utilization -
+             peak_memory) // cache_block_size)
+        num_cpu_blocks = int(self.cache_config.swap_space_bytes //
+                             cache_block_size)
+        num_gpu_blocks = max(num_gpu_blocks, 0)
+        num_cpu_blocks = max(num_cpu_blocks, 0)
+        gc.collect()
+        torch.xpu.empty_cache()
+        return num_gpu_blocks, num_cpu_blocks
+
+    def _warm_up_model(self) -> None:
+        # IPEX don't support capture graph yet
+        pass
+
+    def init_worker_distributed_environment(self) -> None:
+        """Initialize the distributed environment."""
+
+        parallel_config = self.parallel_config
+        rank = self.rank
+        distributed_init_method = self.distributed_init_method
+
+        if torch.distributed.is_initialized():
+            torch_world_size = torch.distributed.get_world_size()
+            if torch_world_size != parallel_config.world_size:
+                raise RuntimeError(
+                    "torch.distributed is already initialized but the torch "
+                    "world size does not match parallel_config.world_size "
+                    f"({torch_world_size} vs. {parallel_config.world_size}).")
+        elif not distributed_init_method:
+            raise ValueError(
+                "distributed_init_method must be set if torch.distributed "
+                "is not already initialized")
+        else:
+            # use sockets as default Level zero IPC exchange backend. By
+            # default oneccl will use `drmfd` as mechanism which need extra
+            # dependency (libdrm and drm headers) on your system.
+            ENV_CCL_ATL_TRANSPORT = os.getenv("CCL_ATL_TRANSPORT", "ofi")
+            ENV_LOCAL_WORLD_SIZE = os.getenv("LOCAL_WORLD_SIZE",
+                                             str(parallel_config.world_size))
+            os.environ["CCL_ATL_TRANSPORT"] = ENV_CCL_ATL_TRANSPORT
+            os.environ["LOCAL_WORLD_SIZE"] = ENV_LOCAL_WORLD_SIZE
+            os.environ["LOCAL_RANK"] = str(self.local_rank)
+            init_distributed_environment(
+                world_size=parallel_config.world_size,
+                rank=rank,
+                distributed_init_method=distributed_init_method,
+                local_rank=self.local_rank,
+                backend="ccl")
+
+        ensure_model_parallel_initialized(
+            parallel_config.tensor_parallel_size,
+            parallel_config.pipeline_parallel_size)
+        # global all_reduce needed for overall oneccl warm up
+        torch.distributed.all_reduce(torch.zeros(1).xpu())
+
+        if parallel_config.pipeline_parallel_size > 1:
+            # Add pp group init to avoid
+            # p2p communication as the first call
+            get_pp_group().all_reduce(torch.zeros(1).xpu())