[Platform] Refactor Platform attention backend selection to avoid breakpoint for OOT platform

vllm/attention/selector.py

@@ -3,11 +3,11 @@
 
 import inspect
 from functools import cache
-from typing import cast, get_args
+from typing import NamedTuple, cast, get_args
 
 import torch
 
-from vllm.attention.backends.abstract import AttentionBackend
+from vllm.attention.backends.abstract import AttentionBackend, AttentionType
 from vllm.attention.backends.registry import (
     MAMBA_TYPE_TO_BACKEND_MAP,
     MambaAttentionBackendEnum,
@@ -19,6 +19,30 @@
 logger = init_logger(__name__)
 
 
+class AttentionSelectorConfig(NamedTuple):
+    head_size: int
+    dtype: torch.dtype
+    kv_cache_dtype: CacheDType | None
+    block_size: int | None
+    use_mla: bool = False
+    has_sink: bool = False
+    use_sparse: bool = False
+    use_mm_prefix: bool = False
+    attn_type: str = AttentionType.DECODER
+
+    def __repr__(self):
+        return (
+            f"AttentionSelectorConfig(head_size={self.head_size}, "
+            f"dtype={self.dtype}, "
+            f"kv_cache_dtype={self.kv_cache_dtype}, "
+            f"block_size={self.block_size}, "
+            f"use_mla={self.use_mla}, "
+            f"has_sink={self.has_sink}, "
+            f"use_sparse={self.use_sparse}, "
+            f"attn_type={self.attn_type})"
+        )
+
+
 def get_attn_backend(
     head_size: int,
     dtype: torch.dtype,
@@ -44,8 +68,7 @@ def get_attn_backend(
     vllm_config = get_current_vllm_config()
     backend_enum = vllm_config.attention_config.backend
 
-    return _cached_get_attn_backend(
-        backend=backend_enum,
+    attn_selector_config = AttentionSelectorConfig(
         head_size=head_size,
         dtype=dtype,
         kv_cache_dtype=cast(CacheDType | None, kv_cache_dtype),
@@ -54,22 +77,19 @@ def get_attn_backend(
         has_sink=has_sink,
         use_sparse=use_sparse,
         use_mm_prefix=use_mm_prefix,
-        attn_type=attn_type,
+        attn_type=attn_type or AttentionType.DECODER,
+    )
+
+    return _cached_get_attn_backend(
+        backend=backend_enum,
+        attn_selector_config=attn_selector_config,
     )
 
 
 @cache
 def _cached_get_attn_backend(
     backend,
-    head_size: int,
-    dtype: torch.dtype,
-    kv_cache_dtype: CacheDType | None,
-    block_size: int | None,
-    use_mla: bool = False,
-    has_sink: bool = False,
-    use_sparse: bool = False,
-    use_mm_prefix: bool = False,
-    attn_type: str | None = None,
+    attn_selector_config: AttentionSelectorConfig,
 ) -> type[AttentionBackend]:
     from vllm.platforms import current_platform
 
@@ -82,29 +102,13 @@ def _cached_get_attn_backend(
         )
         attention_cls = current_platform.get_attn_backend_cls(
             backend,
-            head_size,
-            dtype,
-            kv_cache_dtype,
-            block_size,
-            True,  # use_v1
-            use_mla,
-            has_sink,
-            use_sparse,
-            use_mm_prefix,
-            attn_type,
+            use_v1=True,  # use_v1
+            **attn_selector_config._asdict(),
         )
     else:
         attention_cls = current_platform.get_attn_backend_cls(
             backend,
-            head_size,
-            dtype,
-            kv_cache_dtype,
-            block_size,
-            use_mla,
-            has_sink,
-            use_sparse,
-            use_mm_prefix,
-            attn_type,
+            attn_selector_config=attn_selector_config,
         )
     if not attention_cls:
         raise ValueError(

vllm/platforms/cpu.py

@@ -23,6 +23,7 @@
 logger = init_logger(__name__)
 
 if TYPE_CHECKING:
+    from vllm.attention.selector import AttentionSelectorConfig
     from vllm.config import VllmConfig
 else:
     VllmConfig = None
@@ -126,21 +127,13 @@ def get_device_name(cls, device_id: int = 0) -> str:
     def get_attn_backend_cls(
         cls,
         selected_backend: "AttentionBackendEnum",
-        head_size: int,
-        dtype: torch.dtype,
-        kv_cache_dtype: str | None,
-        block_size: int,
-        use_mla: bool,
-        has_sink: bool,
-        use_sparse: bool,
-        use_mm_prefix: bool,
-        attn_type: str | None = None,
+        attn_selector_config: "AttentionSelectorConfig",
     ) -> str:
         if selected_backend and selected_backend != AttentionBackendEnum.CPU_ATTN:
             logger.info("Cannot use %s backend on CPU.", selected_backend)
-        if use_mla:
+        if attn_selector_config.use_mla:
             raise NotImplementedError("MLA is not supported on CPU.")
-        if use_sparse:
+        if attn_selector_config.use_sparse:
             raise NotImplementedError("Sparse Attention is not supported on CPU.")
         return AttentionBackendEnum.CPU_ATTN.get_path()
 

vllm/platforms/cuda.py

@@ -14,7 +14,6 @@
 
 # import custom ops, trigger op registration
 import vllm._C  # noqa
-from vllm.attention.backends.abstract import AttentionType
 from vllm.attention.backends.registry import AttentionBackendEnum
 from vllm.logger import init_logger
 from vllm.utils.import_utils import import_pynvml
@@ -23,6 +22,7 @@
 from .interface import DeviceCapability, Platform, PlatformEnum
 
 if TYPE_CHECKING:
+    from vllm.attention.selector import AttentionSelectorConfig
     from vllm.config import VllmConfig
     from vllm.config.cache import CacheDType
 else:
@@ -275,38 +275,24 @@ def get_vit_attn_backend(
     @classmethod
     def get_valid_backends(
         cls,
-        head_size,
-        dtype,
-        kv_cache_dtype,
-        block_size,
-        use_mla,
-        has_sink,
-        use_sparse,
-        use_mm_prefix,
-        device_capability,
-        attn_type,
+        device_capability: DeviceCapability,
+        attn_selector_config: "AttentionSelectorConfig",
     ) -> tuple[
         list[tuple["AttentionBackendEnum", int]],
         dict["AttentionBackendEnum", list[str]],
     ]:
         valid_backends_priorities = []
         invalid_reasons = {}
 
-        backend_priorities = _get_backend_priorities(use_mla, device_capability)
+        backend_priorities = _get_backend_priorities(
+            attn_selector_config.use_mla, device_capability
+        )
         for priority, backend in enumerate(backend_priorities):
             try:
                 backend_class = backend.get_class()
                 invalid_reasons_i = backend_class.validate_configuration(
-                    head_size,
-                    dtype,
-                    kv_cache_dtype,
-                    block_size,
-                    use_mla,
-                    has_sink,
-                    use_sparse,
-                    use_mm_prefix,
-                    device_capability,
-                    attn_type,
+                    device_capability=device_capability,
+                    **attn_selector_config._asdict(),
                 )
             except ImportError:
                 invalid_reasons_i = ["ImportError"]
@@ -321,19 +307,8 @@ def get_valid_backends(
     def get_attn_backend_cls(
         cls,
         selected_backend: "AttentionBackendEnum",
-        head_size: int,
-        dtype: torch.dtype,
-        kv_cache_dtype: "CacheDType | None",
-        block_size: int | None,
-        use_mla: bool,
-        has_sink: bool,
-        use_sparse: bool,
-        use_mm_prefix: bool,
-        attn_type: str | None = None,
+        attn_selector_config: "AttentionSelectorConfig",
     ) -> str:
-        if attn_type is None:
-            attn_type = AttentionType.DECODER
-
         device_capability = cls.get_device_capability()
         assert device_capability is not None
 
@@ -342,16 +317,8 @@ def get_attn_backend_cls(
             try:
                 backend_class = selected_backend.get_class()
                 invalid_reasons = backend_class.validate_configuration(
-                    head_size,
-                    dtype,
-                    kv_cache_dtype,
-                    None,
-                    use_mla,
-                    has_sink,
-                    use_sparse,
-                    use_mm_prefix,
-                    device_capability,
-                    attn_type,
+                    device_capability=device_capability,
+                    **attn_selector_config._asdict(),
                 )
             except ImportError:
                 invalid_reasons = ["ImportError"]
@@ -367,16 +334,8 @@ def get_attn_backend_cls(
         # No selected backend or the selected backend is invalid,
         # so we try finding a valid backend.
         valid_backends_priorities, invalid_reasons = cls.get_valid_backends(
-            head_size,
-            dtype,
-            kv_cache_dtype,
-            None,
-            use_mla,
-            has_sink,
-            use_sparse,
-            use_mm_prefix,
-            device_capability,
-            attn_type,
+            device_capability=device_capability,
+            attn_selector_config=attn_selector_config,
         )
         reasons_str = (
             "{"
@@ -386,11 +345,7 @@ def get_attn_backend_cls(
             )
             + "}"
         )
-        config_str = (
-            f"head_size: {head_size}, dtype: {dtype}, "
-            f"kv_cache_dtype: {kv_cache_dtype}, block_size: {block_size}, "
-            f"use_mla: {use_mla}, has_sink: {has_sink}, use_sparse: {use_sparse}"
-        )
+        config_str = attn_selector_config.__repr__()
         logger.debug_once(
             f"Some attention backends are not valid for {cls.device_name} with "
             f"{config_str}. Reasons: {reasons_str}."

vllm/platforms/interface.py

@@ -18,8 +18,8 @@
 if TYPE_CHECKING:
     from torch.distributed import PrefixStore, ProcessGroup
 
+    from vllm.attention.selector import AttentionSelectorConfig
     from vllm.config import VllmConfig
-    from vllm.config.cache import CacheDType
     from vllm.inputs import ProcessorInputs, PromptType
     from vllm.pooling_params import PoolingParams
     from vllm.sampling_params import SamplingParams
@@ -232,15 +232,7 @@ def get_vit_attn_backend(
     def get_attn_backend_cls(
         cls,
         selected_backend: "AttentionBackendEnum",
-        head_size: int,
-        dtype: torch.dtype,
-        kv_cache_dtype: "CacheDType | None",
-        block_size: int,
-        use_mla: bool,
-        has_sink: bool,
-        use_sparse: bool,
-        use_mm_prefix: bool,
-        attn_type: str | None = None,
+        attn_selector_config: "AttentionSelectorConfig",
     ) -> str:
         """Get the attention backend class of a device."""
         return ""

vllm/platforms/rocm.py

@@ -15,6 +15,7 @@
 from .interface import DeviceCapability, Platform, PlatformEnum
 
 if TYPE_CHECKING:
+    from vllm.attention.selector import AttentionSelectorConfig
     from vllm.config import VllmConfig
 
 logger = init_logger(__name__)
@@ -208,21 +209,16 @@ def get_vit_attn_backend(
     @classmethod
     def get_attn_backend_cls(
         cls,
-        selected_backend,
-        head_size,
-        dtype,
-        kv_cache_dtype,
-        block_size,
-        use_mla,
-        has_sink,
-        use_sparse,
-        use_mm_prefix,
-        attn_type: str | None = None,
+        selected_backend: "AttentionBackendEnum",
+        attn_selector_config: "AttentionSelectorConfig",
     ) -> str:
         from vllm._aiter_ops import rocm_aiter_ops
 
-        if use_sparse:
-            if kv_cache_dtype.startswith("fp8"):
+        block_size = attn_selector_config.block_size
+        kv_cache_dtype = attn_selector_config.kv_cache_dtype
+
+        if attn_selector_config.use_sparse:
+            if kv_cache_dtype and kv_cache_dtype.startswith("fp8"):
                 raise ValueError(
                     "ROCMAiterMLASparseBackend doesn't support fp8 kv_cache_dtype."
                 )
@@ -232,7 +228,7 @@ def get_attn_backend_cls(
             logger.info_once("Using Sparse MLA backend on V1 engine.")
             return AttentionBackendEnum.ROCM_AITER_MLA_SPARSE.get_path()
 
-        if use_mla:
+        if attn_selector_config.use_mla:
             if selected_backend is None:
                 selected_backend = (
                     AttentionBackendEnum.ROCM_AITER_MLA

vllm/platforms/tpu.py

@@ -16,6 +16,7 @@
 if TYPE_CHECKING:
     from typing import TypeAlias
 
+    from vllm.attention.selector import AttentionSelectorConfig
     from vllm.config import VllmConfig
     from vllm.config.cache import BlockSize
     from vllm.pooling_params import PoolingParams
@@ -57,17 +58,9 @@ def import_kernels(cls) -> None:
     def get_attn_backend_cls(
         cls,
         selected_backend: "AttentionBackendEnum",
-        head_size: int,
-        dtype: torch.dtype,
-        kv_cache_dtype: str | None,
-        block_size: int,
-        use_mla: bool,
-        has_sink: bool,
-        use_sparse: bool,
-        use_mm_prefix: bool,
-        attn_type: str | None = None,
+        attn_selector_config: "AttentionSelectorConfig",
     ) -> str:
-        if use_sparse:
+        if attn_selector_config.use_sparse:
             raise NotImplementedError("Sparse Attention is not supported on TPU.")
         if selected_backend != AttentionBackendEnum.PALLAS:
             logger.info("Cannot use %s backend on TPU.", selected_backend)