Repository: vllm-project/vllm
File: vllm/platforms/cuda.py (Python)

Code before:
                f"Backend {backend} is not supported for vit attention. "
                f"Supported backends are: {cls.get_supported_vit_attn_backends()}"
            )
            logger.info_once(f"Using backend {backend} for vit attention")
            return backend

        cc = cls.get_device_capability()
        for vit_attn_backend in cls.get_supported_vit_attn_backends():
            if vit_attn_backend == AttentionBackendEnum.TORCH_SDPA:
                continue
            try:
                backend_class = vit_attn_backend.get_class()
                is_backend_supported = backend_class.supports_head_size(
                    head_size
                ) and backend_class.supports_dtype(dtype)
                if cc is not None:
                    is_backend_supported = (
                        is_backend_supported
                        and backend_class.supports_compute_capability(cc)
                    )
                if is_backend_supported:
                    logger.info_once(
                        f"Using backend {vit_attn_backend} for vit attention"
                    )
                    return vit_attn_backend
            except ImportError:
                pass

        return AttentionBackendEnum.TORCH_SDPA

    @classmethod
    def get_punica_wrapper(cls) -> str:
        return "vllm.lora.punica_wrapper.punica_gpu.PunicaWrapperGPU"

    @classmethod
    def get_device_communicator_cls(cls) -> str:
        return (
            "vllm.distributed.device_communicators.cuda_communicator.CudaCommunicator"  # noqa
        )

    @classmethod
    def supports_fp8(cls) -> bool:
        return cls.has_device_capability(89)

    @classmethod
    def use_custom_allreduce(cls) -> bool:
        return True

    @classmethod
    def opaque_attention_op(cls) -> bool:
        return True

Review comment (suggestion):
can you help me to add this `AttentionBackendEnum.TRITON_ATTN,` to the `get_supported_vit_attn_backends` of `rocm.py`? I validated, it also works for rocm.

But for now, I don't update the `get_vit_attn_backend`.

Code after:
                f"No valid attention backend found for {cls.device_name} "
                f"with {config_str}. Reasons: {reasons_str}."
            )

        # We have found some valid backends. Select the one with the
        # highest priority.
        sorted_indices = sorted(
            range(len(valid_backends_priorities)),
            key=lambda i: valid_backends_priorities[i][1],
        )
        selected_index = sorted_indices[0]
        selected_backend = valid_backends_priorities[selected_index][0]
        logger.info_once(
            "Using %s attention backend out of potential backends: %s.",
            selected_backend.name,
            "[" + ", ".join(f"'{b[0].name}'" for b in valid_backends_priorities) + "]",
            scope="local",
        )

        return selected_backend.get_path()

    @classmethod
    def get_supported_vit_attn_backends(cls) -> list["AttentionBackendEnum"]:
        return [
            AttentionBackendEnum.FLASH_ATTN,
            AttentionBackendEnum.TRITON_ATTN,
            AttentionBackendEnum.TORCH_SDPA,
        ]

    @classmethod
    def get_vit_attn_backend(
        cls,
        head_size: int,
        dtype: torch.dtype,
        backend: "AttentionBackendEnum | None" = None,
    ) -> "AttentionBackendEnum":
        if backend is not None:
            assert backend in cls.get_supported_vit_attn_backends(), (
                f"Backend {backend} is not supported for vit attention. "
                f"Supported backends are: {cls.get_supported_vit_attn_backends()}"
            )
            logger.info_once(f"Using backend {backend} for vit attention")
            return backend

        cc = cls.get_device_capability()
        for vit_attn_backend in cls.get_supported_vit_attn_backends():
            if vit_attn_backend == AttentionBackendEnum.TORCH_SDPA:
                continue
            try:
                backend_class = vit_attn_backend.get_class()
                is_backend_supported = backend_class.supports_head_size(