add flashmla support

vllm/attention/ops/flashmla.py

@@ -28,13 +28,17 @@ if current_platform.is_cuda():
 else:
     _flashmla_extension_C_AVAILABLE = False
     
+if current_platform.is_rocm():
+    import flash_mla_cuda
+    _flashmla_C_AVAILABLE = True
+
 
 def is_flashmla_supported() -> Tuple[bool, Optional[str]]:
     """
     Return: is_supported_flag, unsupported_reason (optional).
     """
-    if not current_platform.is_cuda():
-        return False, "FlashMLA is only supported on CUDA devices."
+    if not (current_platform.is_cuda() or current_platform.is_rocm()):
+        return False, "FlashMLA is supported on CUDA and ROCM devices."
     if current_platform.get_device_capability()[0] != 9:
         return False, "FlashMLA is only supported on Hopper devices."
     if not _flashmla_C_AVAILABLE:
@@ -71,11 +75,18 @@ def get_mla_metadata(
             (num_sm_parts, TileSchedulerMetaDataSize), dtype torch.int32.
     - num_splits: (batch_size + 1), dtype torch.int32.
     """
+        
+    if current_platform.is_rocm():
+        return flash_mla_cuda.get_mla_metadata(cache_seqlens,
+                                num_q_tokens_per_head_k,
+                                num_heads_k)
+    else:
         return torch.ops._flashmla_C.get_mla_decoding_metadata(
         cache_seqlens, num_q_tokens_per_head_k, num_heads_k, num_heads_q,
         is_fp8_kvcache, topk)
 
 
+
 def flash_mla_with_kvcache(
     q: torch.Tensor,
     k_cache: torch.Tensor,
@@ -140,6 +151,11 @@ def flash_mla_with_kvcache(
         out, softmax_lse = torch.ops._flashmla_extension_C.fwd_kvcache_mla_fp8(
             q, k_cache, head_dim_v, cache_seqlens, block_table, softmax_scale,
             causal, tile_scheduler_metadata, num_splits, descale_q, descale_k)
+    else:
+        if current_platform.is_rocm():
+            out, softmax_lse = flash_mla_cuda.fwd_kvcache_mla(
+                q, k_cache, block_table, cache_seqlens, head_dim_v, tile_scheduler_metadata,
+                num_splits, softmax_scale, causal)
         else:
             out, softmax_lse = torch.ops._flashmla_C.fwd_kvcache_mla(
                 q, k_cache, head_dim_v, cache_seqlens, block_table, softmax_scale,

vllm/envs.py

@@ -204,6 +204,7 @@ if TYPE_CHECKING:
     VLLM_USE_NCCL_SYMM_MEM: bool = False
     VLLM_NCCL_INCLUDE_PATH: Optional[str] = None
     VLLM_USE_FBGEMM: bool = False
+    VLLM_USE_FLASH_MLA: bool = False
 
 
 def get_default_cache_root():
@@ -1469,6 +1470,11 @@ environment_variables: dict[str, Callable[[], Any]] = {
     lambda: os.environ.get("VLLM_NCCL_INCLUDE_PATH", None),
     # Flag to enable FBGemm kernels on model execution
     "VLLM_USE_FBGEMM": lambda: bool(int(os.getenv("VLLM_USE_FBGEMM", "0"))),
+    
+    # If set, vLLM will use FLASH MLA attention optimizations.
+    "VLLM_USE_FLASH_MLA":
+    lambda: bool(int(os.getenv("VLLM_USE_FLASH_MLA", "0"))),
+
 }
 
 # --8<-- [end:env-vars-definition]

vllm/platforms/rocm.py

@@ -136,33 +136,34 @@ def use_rocm_custom_paged_attention(
         alibi_slopes: Optional[torch.Tensor] = None,
         sinks: Optional[torch.Tensor] = None) -> bool:
 
-    GPU_ARCH = torch.cuda.get_device_properties("cuda").gcnArchName
-    ON_GFX9 = any(arch in GPU_ARCH for arch in ["gfx90a", "gfx942", "gfx950"])
-    ON_GFX11_GFX12 = any(arch in GPU_ARCH for arch in ["gfx11", "gfx12"])
+    # GPU_ARCH = torch.cuda.get_device_properties("cuda").gcnArchName
+    # ON_GFX9 = any(arch in GPU_ARCH for arch in ["gfx90a", "gfx942", "gfx950"])
+    # ON_GFX11_GFX12 = any(arch in GPU_ARCH for arch in ["gfx11", "gfx12"])
 
     # custom paged attn always supported on V0. On V1, requires sliding window
     # disabled due to observed numerical discrepancy.
-    if ON_GFX9:
-        return ((not envs.VLLM_USE_V1 or sliding_window == 0
-                 or sliding_window == (-1, -1))
-                and (qtype == torch.half or qtype == torch.bfloat16)
-                and (head_size == 64 or head_size == 128)
-                and (block_size == 16 or block_size == 32)
-                and (gqa_ratio >= 1 and gqa_ratio <= 16)
-                and max_seq_len <= 128 * 1024
-                and (envs.VLLM_ROCM_CUSTOM_PAGED_ATTN)
-                and not (envs.VLLM_ROCM_USE_AITER_PAGED_ATTN
-                         and envs.VLLM_ROCM_USE_AITER) and sinks is None)
-
-    else:
-        return (ON_GFX11_GFX12 and (not envs.VLLM_USE_V1 or sliding_window == 0
-                                    or sliding_window == (-1, -1))
-                and (qtype == torch.half or qtype == torch.bfloat16)
-                and head_size == 128 and block_size == 16
-                and (gqa_ratio >= 3 and gqa_ratio <= 16)
-                and max_seq_len <= 128 * 1024 and alibi_slopes is None
-                and kv_cache_dtype == "auto"
-                and envs.VLLM_ROCM_CUSTOM_PAGED_ATTN and sinks is None)
+    # if ON_GFX9:
+    #     return ((not envs.VLLM_USE_V1 or sliding_window == 0
+    #              or sliding_window == (-1, -1))
+    #             and (qtype == torch.half or qtype == torch.bfloat16)
+    #             and (head_size == 64 or head_size == 128)
+    #             and (block_size == 16 or block_size == 32)
+    #             and (gqa_ratio >= 1 and gqa_ratio <= 16)
+    #             and max_seq_len <= 128 * 1024
+    #             and (envs.VLLM_ROCM_CUSTOM_PAGED_ATTN)
+    #             and not (envs.VLLM_ROCM_USE_AITER_PAGED_ATTN
+    #                      and envs.VLLM_ROCM_USE_AITER) and sinks is None)
+
+    # else:
+    #     return (ON_GFX11_GFX12 and (not envs.VLLM_USE_V1 or sliding_window == 0
+    #                                 or sliding_window == (-1, -1))
+    #             and (qtype == torch.half or qtype == torch.bfloat16)
+    #             and head_size == 128 and block_size == 16
+    #             and (gqa_ratio >= 3 and gqa_ratio <= 16)
+    #             and max_seq_len <= 128 * 1024 and alibi_slopes is None
+    #             and kv_cache_dtype == "auto"
+    #             and envs.VLLM_ROCM_CUSTOM_PAGED_ATTN and sinks is None)
+    return False
 
 
 class RocmPlatform(Platform):
@@ -222,14 +223,15 @@ class RocmPlatform(Platform):
                 raise ValueError(
                     f" The selected backend, {selected_backend.name},"
                     f"does not support block size {block_size}.")
-            if selected_backend == _Backend.ROCM_AITER_MLA:
-                if block_size == 1:
-                    logger.info("Using AITER MLA backend on V1 engine.")
-                    return "vllm.v1.attention.backends.mla.rocm_aiter_mla.AiterMLABackend"  # noqa: E501
-                raise ValueError(
-                    f" The selected backend, {selected_backend.name},"
-                    f"does not support block size {block_size}."
-                    "(currently only supports block size 1)")
+            # if selected_backend == _Backend.ROCM_AITER_MLA:
+            #     if block_size == 1:
+            #         logger.info("Using AITER MLA backend on V1 engine.")
+            #         return "vllm.v1.attention.backends.mla.rocm_aiter_mla.AiterMLABackend"  # noqa: E501
+            #     raise ValueError(
+            #         f" The selected backend, {selected_backend.name},"
+            #         f"does not support block size {block_size}."
+            #         "(currently only supports block size 1)")
+            
             raise ValueError(
                 f" The selected backend, {selected_backend.name},"
                 f"is not MLA type while requested for MLA backend.")
@@ -249,6 +251,21 @@ class RocmPlatform(Platform):
                 logger.info("Using Rocm/Aiter Attention backend on V1 engine.")
                 return ("vllm.v1.attention.backends."
                         "rocm_attn.RocmAttentionBackend")
+            if envs.VLLM_USE_FLASH_MLA:
+                from vllm.attention.ops.flashmla import is_flashmla_supported
+                use_flashmla = selected_backend == _Backend.FLASHMLA or (
+                    selected_backend is None and is_flashmla_supported()[0])
+                
+                if use_flashmla:
+                    if block_size != 64:
+                        logger.warning(
+                            "FlashMLA backend is not supported for block size %d"
+                            " (currently only supports block size 64).",
+                            block_size)
+                    else:
+                        logger.info_once("Using FlashMLA backend on V1 engine.")
+                        return ("vllm.v1.attention.backends.mla."
+                                "flashmla.FlashMLABackend")
             else:
                 # default case, using triton unified attention
                 logger.info("Using Triton Attention backend on V1 engine.")