[FEAT][ROCm] Enable running Flash Attention as ViT attn backend for Qwen-VL models on ROCm platform. (#22069)

Signed-off-by: tjtanaavllm <tunjian.tan@amd.com>
Signed-off-by: vllmellm <vllm.ellm@embeddedllm.com>
Co-authored-by: tjtanaavllm <tunjian.tan@amd.com>

vllm/platforms/rocm.py

@@ -173,6 +173,18 @@ class RocmPlatform(Platform):
         "quark", "ptpc_fp8"
     ]
 
+    @classmethod
+    def get_vit_attn_backend(cls, support_fa: bool = False) -> _Backend:
+        if support_fa:
+            if (envs.VLLM_ROCM_USE_AITER and envs.VLLM_ROCM_USE_AITER_MHA
+                    and on_gfx9()):
+                # Note: AITER FA is only supported for Qwen-VL models.
+                # TODO: Add support for other VL models in their model class.
+                return _Backend.ROCM_AITER_FA
+            if on_gfx9():
+                return _Backend.FLASH_ATTN
+        return _Backend.TORCH_SDPA
+
     @classmethod
     def get_attn_backend_cls(cls, selected_backend, head_size, dtype,
                              kv_cache_dtype, block_size, use_v1,