[UX] Add --moe-backend arg for explicit kernel selection (#33807)

Signed-off-by: mgoin <mgoin64@gmail.com>
Co-authored-by: Robert Shaw <114415538+robertgshaw2-redhat@users.noreply.github.com>

vllm/config/kernel.py

@@ -2,13 +2,25 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
 from collections.abc import Callable
-from typing import Any
+from typing import Any, Literal
 
 from pydantic import Field, field_validator
 
 from vllm.config.utils import config
 from vllm.utils.hashing import safe_hash
 
+MoEBackend = Literal[
+    "auto",
+    "triton",
+    "deep_gemm",
+    "cutlass",
+    "flashinfer_trtllm",
+    "flashinfer_cutlass",
+    "flashinfer_cutedsl",
+    "marlin",
+    "aiter",
+]
+
 
 @config
 class KernelConfig:
@@ -17,6 +29,26 @@ class KernelConfig:
     enable_flashinfer_autotune: bool = Field(default=None)
     """If True, run FlashInfer autotuning during kernel warmup."""
 
+    moe_backend: MoEBackend = "auto"
+    """Backend for MoE expert computation kernels. Available options:
+
+    - "auto": Automatically select the best backend based on model and hardware\n
+    - "triton": Use Triton-based fused MoE kernels\n
+    - "deep_gemm": Use DeepGEMM kernels (FP8 block-quantized only)\n
+    - "cutlass": Use vLLM CUTLASS kernels\n
+    - "flashinfer_trtllm": Use FlashInfer with TRTLLM-GEN kernels\n
+    - "flashinfer_cutlass": Use FlashInfer with CUTLASS kernels\n
+    - "flashinfer_cutedsl": Use FlashInfer with CuteDSL kernels (FP4 only)\n
+    - "marlin": Use Marlin kernels (weight-only quantization)\n
+    - "aiter": Use AMD AITer kernels (ROCm only)"""
+
+    @field_validator("moe_backend", mode="before")
+    @classmethod
+    def _normalize_moe_backend(cls, value: Any) -> Any:
+        if isinstance(value, str):
+            return value.lower().replace("-", "_")
+        return value
+
     def compute_hash(self) -> str:
         """
         WARNING: Whenever a new field is added to this config,