[BugFix] Fix IMA FlashMLA full cuda-graph and DP + Update FlashMLA (#21691)

Signed-off-by: Lucas Wilkinson <lwilkins@redhat.com>
Co-authored-by: yewentao256 <zhyanwentao@126.com>
Co-authored-by: Wentao Ye <44945378+yewentao256@users.noreply.github.com>

cmake/external_projects/flashmla.cmake

@@ -19,7 +19,7 @@ else()
   FetchContent_Declare(
         flashmla
         GIT_REPOSITORY https://github.com/vllm-project/FlashMLA.git
-        GIT_TAG 575f7724b9762f265bbee5889df9c7d630801845
+        GIT_TAG 0e43e774597682284358ff2c54530757b654b8d1
         GIT_PROGRESS TRUE
         CONFIGURE_COMMAND ""
         BUILD_COMMAND ""
@@ -37,9 +37,9 @@ cuda_archs_loose_intersection(FLASH_MLA_ARCHS "9.0a" "${CUDA_ARCHS}")
 if(${CMAKE_CUDA_COMPILER_VERSION} VERSION_GREATER 12.3 AND FLASH_MLA_ARCHS)
     set(FlashMLA_SOURCES
         ${flashmla_SOURCE_DIR}/csrc/flash_api.cpp
-        ${flashmla_SOURCE_DIR}/csrc/flash_fwd_mla_bf16_sm90.cu
-        ${flashmla_SOURCE_DIR}/csrc/flash_fwd_mla_fp16_sm90.cu
-        ${flashmla_SOURCE_DIR}/csrc/flash_fwd_mla_metadata.cu)
+        ${flashmla_SOURCE_DIR}/csrc/kernels/splitkv_mla.cu
+        ${flashmla_SOURCE_DIR}/csrc/kernels/mla_combine.cu
+        ${flashmla_SOURCE_DIR}/csrc/kernels/get_mla_metadata.cu)
 
     set(FlashMLA_INCLUDES
         ${flashmla_SOURCE_DIR}/csrc/cutlass/include

vllm/attention/ops/flashmla.py

@@ -91,7 +91,6 @@ def flash_mla_with_kvcache(
     out, softmax_lse = torch.ops._flashmla_C.fwd_kvcache_mla(
         q,
         k_cache,
-        None,
         head_dim_v,
         cache_seqlens,
         block_table,

vllm/v1/attention/backends/mla/flashmla.py

@@ -70,6 +70,22 @@ class FlashMLAMetadataBuilder(MLACommonMetadataBuilder[FlashMLAMetadata]):
         self.cg_buf_tile_scheduler_metadata = None
         self.cg_buf_num_splits = None
 
+        device_properties = torch.cuda.get_device_properties(self.device)
+        num_sms = device_properties.multi_processor_count
+
+        if self.compilation_config.full_cuda_graph:
+            self.cg_buf_tile_scheduler_metadata = torch.zeros(
+                # Upper bound on size (<= #SMs, TileSchedulerMetaDataSize)
+                # TileSchedulerMetaDataSize = 8
+                (num_sms, 8),
+                device=self.device,
+                dtype=torch.int32,
+            )
+            self.cg_buf_num_splits = torch.empty(
+                (vllm_config.scheduler_config.max_num_seqs + 1),
+                device=self.device,
+                dtype=torch.int32)
+
     def _build_decode(self, block_table_tensor: torch.Tensor,
                       seq_lens: torch.Tensor) -> FlashMLADecodeMetadata:
         tile_scheduler_metadata, num_splits = \
@@ -80,19 +96,16 @@ class FlashMLAMetadataBuilder(MLACommonMetadataBuilder[FlashMLAMetadata]):
         )
 
         if self.compilation_config.full_cuda_graph:
-            # First time around (CUDAGraph capture), allocate the static buffer
-            if self.cg_buf_tile_scheduler_metadata is None:
-                self.cg_buf_tile_scheduler_metadata = tile_scheduler_metadata
-                self.cg_buf_num_splits = num_splits
-            else:
+            assert self.cg_buf_tile_scheduler_metadata is not None
             assert self.cg_buf_num_splits is not None
 
-                # Metadata per-SM, fixed size (#SMs, TileMetadataSize)
-                assert (self.cg_buf_tile_scheduler_metadata.size() ==
-                        tile_scheduler_metadata.size())
-                self.cg_buf_tile_scheduler_metadata.\
-                    copy_(tile_scheduler_metadata)
-                tile_scheduler_metadata = self.cg_buf_tile_scheduler_metadata
+            sm_parts = tile_scheduler_metadata.size(0)
+            # Metadata per-SM, upper bound on size (<= #SMs, TileMetadataSize)
+            assert sm_parts <= self.cg_buf_tile_scheduler_metadata.size(0)
+            tile_scheduler_metadata_view = \
+                self.cg_buf_tile_scheduler_metadata[:sm_parts]
+            tile_scheduler_metadata_view.copy_(tile_scheduler_metadata)
+            tile_scheduler_metadata = tile_scheduler_metadata_view
 
             # Num splits is per-batch, varying size (batch_size,)
             n = num_splits.size(0)
@@ -100,7 +113,10 @@ class FlashMLAMetadataBuilder(MLACommonMetadataBuilder[FlashMLAMetadata]):
             assert n <= self.cg_buf_num_splits.size(0)
             num_splits_view = self.cg_buf_num_splits[:n]
             num_splits_view.copy_(num_splits)
-                self.cg_buf_num_splits[n:].fill_(0)  # fill the rest with 0s
+            # Num splits needs to monotonically increasing
+            # (with: https://github.com/vllm-project/FlashMLA/pull/3, otherwise
+            #  it needs to monotonically increasing by 1)
+            self.cg_buf_num_splits[n:].fill_(num_splits[-1])
             num_splits = num_splits_view
 
         return FlashMLADecodeMetadata(