[Model Runner V2] Support FlashInfer backend & Fix CUDA Graph bug [1/2] (#32348)

Signed-off-by: Woosuk Kwon <woosuk.kwon@berkeley.edu>

vllm/v1/worker/gpu/cudagraph_utils.py

@@ -195,14 +195,18 @@ def get_cudagraph_size(
     cudagraph_sizes: dict[int, int],
     cudagraph_mode: CUDAGraphMode,
 ) -> int | None:
+    if not cudagraph_mode.has_full_cudagraphs():
+        # No full CUDA graph is used.
+        return None
+
     size = cudagraph_sizes.get(num_tokens_after_dp_padding)
     if size is None:
         # No CUDA graph for this size.
         return None
-    if cudagraph_mode == CUDAGraphMode.FULL_DECODE_ONLY:
-        all_decode = all(x == 1 for x in num_tokens_per_request)
-        if not all_decode:
-            # Prefill is included.
+
+    is_mixed = any(x > 1 for x in num_tokens_per_request)
+    if is_mixed and cudagraph_mode.mixed_mode() != CUDAGraphMode.FULL:
+        # Prefill is included, and this mode doesn't use CUDA graph for it.
         return None
     return size
 

vllm/v1/worker/gpu/model_runner.py

@@ -230,8 +230,14 @@ class GPUModelRunner(LoRAModelRunnerMixin, KVConnectorModelRunnerMixin):
             )
 
         # TODO(woosuk): Support other backends.
-        if not all(b.get_name() == "FLASH_ATTN" for b in self.attn_backends.values()):
-            raise NotImplementedError("Only FLASH_ATTN backend is supported currently.")
+        supported_backends = ("FLASH_ATTN", "FLASHINFER")
+        for backend in self.attn_backends.values():
+            backend_name = backend.get_name()
+            if backend_name not in supported_backends:
+                raise NotImplementedError(
+                    f"The {backend_name} attention backend is not supported yet. "
+                    f"Supported backends are: {supported_backends}."
+                )
 
         self.kv_caches: list[torch.Tensor] = []
         init_kv_cache(