[NVIDIA] Add SM100 Flashinfer Cutlass MoE fp8 backend (#22357)

Signed-off-by: Amir Klein <203507526+amirkl94@users.noreply.github.com>

.buildkite/test-pipeline.yaml

@@ -630,6 +630,7 @@ steps:
   - vllm/model_executor/layers/fused_moe/cutlass_moe.py
   - vllm/model_executor/layers/fused_moe/flashinfer_cutlass_moe.py
   - vllm/model_executor/layers/fused_moe/flashinfer_cutlass_prepare_finalize.py
+  - vllm/model_executor/layers/quantization/utils/flashinfer_utils.py
   - vllm/v1/attention/backends/flashinfer.py
   - vllm/compilation/fusion.py
   - vllm/compilation/fusion_attn.py
@@ -650,6 +651,7 @@ steps:
     # Fusion
     - pytest -v -s tests/compile/test_fusion_all_reduce.py
     - pytest -v -s tests/compile/test_fusion_attn.py::test_attention_quant_pattern
+    - pytest -v -s tests/kernels/moe/test_flashinfer.py
 
 #####  1 GPU test  #####
 #####  multi gpus test  #####

tests/kernels/moe/test_flashinfer.py

+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+from dataclasses import dataclass
+
+import pytest
+import torch
+
+from vllm.config import ParallelConfig, VllmConfig, set_current_vllm_config
+from vllm.model_executor.layers.fused_moe.fused_moe import fused_experts
+from vllm.model_executor.layers.fused_moe.layer import FusedMoE
+from vllm.model_executor.layers.quantization.utils.flashinfer_utils import (
+    apply_flashinfer_per_tensor_scale_fp8, flashinfer_cutlass_moe_fp8,
+    register_moe_scaling_factors, rotate_flashinfer_fp8_moe_weights,
+    swap_w13_to_w31)
+from vllm.model_executor.layers.quantization.utils.fp8_utils import (
+    input_to_float8)
+from vllm.model_executor.models.llama4 import Llama4MoE
+from vllm.platforms import current_platform
+from vllm.utils.flashinfer import has_flashinfer_cutlass_fused_moe
+
+if not has_flashinfer_cutlass_fused_moe(
+) or not current_platform.has_device_capability(100):
+    pytest.skip("Requires flashinfer_cutlass_fused_moe and nvfp4 support",
+                allow_module_level=True)
+
+NUM_EXPERTS = [16]
+TOP_KS = [1]
+
+MNK_FACTORS = [
+    (256, 8192, 5120),
+    (256, 4096, 5120),
+    (127, 8192, 5120),
+    (127, 4096, 5120),
+    (10, 8192, 5120),
+    (10, 4096, 5120),
+    (1, 8192, 5120),
+    (1, 4096, 5120),
+]
+
+vllm_config = VllmConfig(parallel_config=ParallelConfig(
+    pipeline_parallel_size=1))
+vllm_config.scheduler_config.max_num_seqs = 128
+vllm_config.scheduler_config.max_model_len = 8192
+
+
+def quant_fp8_per_tensor_batches(a):
+    num_batches = a.size(0)
+    a_quant = []
+    a_scales = []
+
+    for i in range(num_batches):
+        a_fp8, a_global_sf = input_to_float8(a[i])
+        a_global_sf = 1.0 / a_global_sf
+        a_quant.append(a_fp8)
+        a_scales.append(a_global_sf)
+
+    result_a_quant = torch.stack(a_quant)
+    result_a_scales = torch.stack(a_scales)
+
+    return result_a_quant, result_a_scales
+
+
+@dataclass
+class TestData:
+    hidden_states: torch.Tensor
+    w13_quantized: torch.Tensor
+    w2_quantized: torch.Tensor
+    a1_scale: torch.Tensor
+    a2_scale: torch.Tensor
+    w13_weight_scale: torch.Tensor
+    w2_weight_scale: torch.Tensor
+    layer: torch.nn.Module
+
+    @staticmethod
+    def make_moe_tensors_8bit(m: int, k: int, n: int, e: int,
+                              reorder: bool) -> "TestData":
+        hidden_states = torch.randn(
+            (m, k), device="cuda", dtype=torch.bfloat16) / 10
+        w13 = torch.randn((e, 2 * n, k), device="cuda", dtype=torch.bfloat16)
+        w2 = torch.randn((e, k, n), device="cuda", dtype=torch.bfloat16)
+
+        # Scale to fp8
+        _, a1_scale = input_to_float8(hidden_states)
+        a1_scale = 1.0 / a1_scale
+        a2_scale = torch.scalar_tensor(1.0).to(device="cuda").to(
+            dtype=torch.float32)
+        w13_quantized, w13_weight_scale = quant_fp8_per_tensor_batches(w13)
+        w2_quantized, w2_weight_scale = quant_fp8_per_tensor_batches(w2)
+
+        layer = torch.nn.Module()
+        layer.w13_weight = w13_quantized.clone()
+        layer.w2_weight = w2_quantized.clone()
+        layer.w13_input_scale = a1_scale
+        layer.w2_input_scale = a2_scale
+        layer.w13_weight_scale = w13_weight_scale
+        layer.w2_weight_scale = w2_weight_scale
+
+        register_moe_scaling_factors(layer)
+
+        # flashinfer expects swapped rows for w13
+        layer.w13_weight.data = swap_w13_to_w31(layer.w13_weight.data)
+        if reorder:
+            rotate_flashinfer_fp8_moe_weights(layer.w13_weight,
+                                              layer.w2_weight)
+        layer.custom_routing_function = Llama4MoE.custom_routing_function
+        layer.intermediate_size_per_partition = n
+        layer.ep_rank = 0
+        layer.local_num_experts = e
+
+        return TestData(
+            hidden_states=hidden_states,
+            w13_quantized=w13_quantized,
+            w2_quantized=w2_quantized,
+            a1_scale=a1_scale,
+            a2_scale=a2_scale,
+            w13_weight_scale=w13_weight_scale,
+            w2_weight_scale=w2_weight_scale,
+            layer=layer,
+        )
+
+
+@pytest.mark.parametrize("m,n,k", MNK_FACTORS)
+@pytest.mark.parametrize("e", NUM_EXPERTS)
+@pytest.mark.parametrize("topk", TOP_KS)
+def test_flashinfer_per_tensor_moe_fp8_no_graph(
+    m: int,
+    n: int,
+    k: int,
+    e: int,
+    topk: int,
+    monkeypatch,
+):
+    current_platform.seed_everything(7)
+    monkeypatch.setenv("VLLM_FUSED_MOE_CHUNK_SIZE", "8192")
+    with set_current_vllm_config(vllm_config):
+        td = TestData.make_moe_tensors_8bit(m, k, n, e, reorder=True)
+
+        score = torch.randn((m, e), device="cuda", dtype=torch.bfloat16)
+        topk_weights, topk_ids = FusedMoE.select_experts(
+            hidden_states=td.hidden_states,
+            router_logits=score,
+            use_grouped_topk=False,
+            top_k=topk,
+            renormalize=False,
+            custom_routing_function=Llama4MoE.custom_routing_function,
+            scoring_func="softmax")
+
+        output = fused_experts(
+            td.hidden_states,
+            td.w13_quantized,
+            td.w2_quantized,
+            topk_weights=topk_weights,
+            topk_ids=topk_ids,
+            inplace=False,
+            activation="silu",
+            use_fp8_w8a8=True,
+            per_channel_quant=False,
+            global_num_experts=e,
+            expert_map=None,
+            w1_scale=td.w13_weight_scale,
+            w2_scale=td.w2_weight_scale,
+            a1_scale=td.a1_scale,
+            a2_scale=td.a2_scale,
+            apply_router_weight_on_input=True,
+        )
+
+        flashinfer_output = apply_flashinfer_per_tensor_scale_fp8(
+            layer=td.layer,
+            hidden_states=td.hidden_states,
+            router_logits=score,
+            routing_bias=None,
+            global_num_experts=e,
+            top_k=topk,
+            num_expert_group=None,
+            topk_group=None,
+            apply_router_weight_on_input=True)
+
+        torch.testing.assert_close(output,
+                                   flashinfer_output,
+                                   atol=5.5e-2,
+                                   rtol=1e-2)
+
+
+@pytest.mark.skip(
+    "Requires flashinfer version that contains https://github.com/flashinfer-ai/flashinfer/pull/1472"
+)
+@pytest.mark.parametrize("m,n,k", MNK_FACTORS)
+@pytest.mark.parametrize("e", NUM_EXPERTS)
+@pytest.mark.parametrize("topk", TOP_KS)
+def test_flashinfer_cutlass_moe_fp8_no_graph(
+    m: int,
+    n: int,
+    k: int,
+    e: int,
+    topk: int,
+    monkeypatch,
+):
+    current_platform.seed_everything(7)
+    monkeypatch.setenv("VLLM_FUSED_MOE_CHUNK_SIZE", "8192")
+    with set_current_vllm_config(vllm_config):
+        td = TestData.make_moe_tensors_8bit(m, k, n, e, reorder=False)
+
+        score = torch.randn((m, e), device="cuda", dtype=torch.bfloat16)
+        topk_weights, topk_ids = FusedMoE.select_experts(
+            hidden_states=td.hidden_states,
+            router_logits=score,
+            use_grouped_topk=False,
+            top_k=topk,
+            renormalize=False,
+            custom_routing_function=Llama4MoE.custom_routing_function,
+            scoring_func="softmax")
+
+        output = fused_experts(
+            td.hidden_states,
+            td.w13_quantized,
+            td.w2_quantized,
+            topk_weights=topk_weights,
+            topk_ids=topk_ids,
+            inplace=False,
+            activation="silu",
+            use_fp8_w8a8=True,
+            per_channel_quant=False,
+            global_num_experts=e,
+            expert_map=None,
+            w1_scale=td.w13_weight_scale,
+            w2_scale=td.w2_weight_scale,
+            a1_scale=td.a1_scale,
+            a2_scale=td.a2_scale,
+            apply_router_weight_on_input=True,
+        )
+
+        td.layer.dp_size = 1
+
+        flashinfer_cutlass_output = flashinfer_cutlass_moe_fp8(
+            td.hidden_states,
+            td.layer,
+            topk_weights,
+            topk_ids,
+            activation="silu",
+            global_num_experts=e,
+            expert_map=None,
+            apply_router_weight_on_input=True,
+        )
+
+        torch.testing.assert_close(output,
+                                   flashinfer_cutlass_output,
+                                   atol=5.5e-2,
+                                   rtol=1e-2)

vllm/model_executor/layers/fused_moe/flashinfer_cutlass_moe.py

@@ -61,8 +61,8 @@ class FlashInferExperts(mk.FusedMoEPermuteExpertsUnpermute):
                 per_act_token_quant=False,
                 block_shape=None,
             ))
-        assert quant_dtype == "nvfp4", ("Only nvfp4 quantization is "
-                                        "currently supported.")
+        assert quant_dtype in ("nvfp4", torch.float8_e4m3fn), (
+            "Only nvfp4,fp8 quantization are currently supported.")
         self.ep_rank = ep_rank
         self.ep_size = ep_size
         self.tp_rank = tp_rank
@@ -122,7 +122,8 @@ class FlashInferExperts(mk.FusedMoEPermuteExpertsUnpermute):
         """
         aq_m, aq_n = aq.shape
         workspace2 = ()
-        output_shape = (aq_m, aq_n * 2)
+        output_shape = (aq_m, aq_n * 2) if self.quant_dtype != \
+            torch.float8_e4m3fn else (aq_m, aq_n)
         workspace_dtype = a.dtype
         workspace1 = output_shape
         # The workspace is determined by `aq`, since it comes after any
@@ -151,14 +152,21 @@ class FlashInferExperts(mk.FusedMoEPermuteExpertsUnpermute):
         expert_tokens_meta: Optional[mk.ExpertTokensMetadata],
         apply_router_weight_on_input: Optional[bool],
     ):
-        # Flashinfer CUTLASS kernel takes scalar global scales,
-        # min because inv_scale.
+        if self.quant_dtype == torch.float8_e4m3fn:
+            quant_scales = [
+                self.g1_alphas, self.a2_gscale, self.g2_alphas, self.a1_gscale
+            ]
 
+            a1q_scale = None  # not passing input_sf in fp8
+            fc1_expert_weights = w1
+            fc2_expert_weights = w2
+        else:
             # Ensure w1_scale and w2_scale are not None before calling view
             assert w1_scale is not None and w2_scale is not None, (
                 "w1_scale and w2_scale must not "
                 "be None for FlashInferExperts")
-
+            # Flashinfer CUTLASS kernel takes scalar global scales,
+            # min because inv_scale.
             quant_scales = [
                 self.a1_gscale,
                 w1_scale.view(torch.int32),
@@ -167,13 +175,16 @@ class FlashInferExperts(mk.FusedMoEPermuteExpertsUnpermute):
                 w2_scale.view(torch.int32),
                 self.g2_alphas,
             ]
+            # FlashInfer API requires weight to be long for nvfp4
+            fc1_expert_weights = w1.view(torch.long)
+            fc2_expert_weights = w2.view(torch.long)
+
         _ = flashinfer_cutlass_fused_moe(
             input=hidden_states,
             token_selected_experts=topk_ids.to(torch.int),
             token_final_scales=topk_weights,
-            # FlashInfer API requires weight to be long for nvfp4
-            fc1_expert_weights=w1.view(torch.long),
-            fc2_expert_weights=w2.view(torch.long),
+            fc1_expert_weights=fc1_expert_weights,
+            fc2_expert_weights=fc2_expert_weights,
             output_dtype=self.out_dtype,
             quant_scales=quant_scales,
             input_sf=a1q_scale,

vllm/model_executor/layers/quantization/fp8.py

@@ -9,6 +9,7 @@ from torch.nn import Module
 from torch.nn.parameter import Parameter
 
 import vllm.envs as envs
+import vllm.model_executor.layers.fused_moe.modular_kernel as mk
 from vllm import _custom_ops as ops
 from vllm.distributed import get_tensor_model_parallel_world_size
 from vllm.logger import init_logger
@@ -23,8 +24,11 @@ from vllm.model_executor.layers.quantization.base_config import (
     QuantizationConfig, QuantizeMethodBase)
 from vllm.model_executor.layers.quantization.kv_cache import BaseKVCacheMethod
 from vllm.model_executor.layers.quantization.utils.flashinfer_utils import (
-    apply_flashinfer_per_tensor_scale_fp8, register_moe_scaling_factors,
-    rotate_flashinfer_fp8_moe_weights, swap_w13_to_w31)
+    FlashinferMoeBackend, apply_flashinfer_per_tensor_scale_fp8,
+    build_flashinfer_fp8_cutlass_moe_prepare_finalize,
+    flashinfer_cutlass_moe_fp8, get_flashinfer_moe_backend,
+    register_moe_scaling_factors, rotate_flashinfer_fp8_moe_weights,
+    select_cutlass_fp8_gemm_impl, swap_w13_to_w31)
 from vllm.model_executor.layers.quantization.utils.fp8_utils import (
     get_col_major_tma_aligned_tensor, requant_weight_ue8m0_inplace)
 from vllm.model_executor.layers.quantization.utils.marlin_utils_fp8 import (
@@ -145,7 +149,7 @@ class Fp8Config(QuantizationConfig):
                 return UnquantizedLinearMethod()
             return Fp8LinearMethod(self)
         elif isinstance(layer, FusedMoE):
-            return Fp8MoEMethod(self, layer.moe_config)
+            return Fp8MoEMethod(self, layer)
         elif isinstance(layer, Attention):
             return Fp8KVCacheMethod(self)
         return None
@@ -482,16 +486,20 @@ class Fp8MoEMethod(FusedMoEMethodBase):
         quant_config: The quantization config.
     """
 
-    def __init__(self, quant_config: Fp8Config, moe: FusedMoEConfig):
-        super().__init__(moe)
+    def __init__(self, quant_config: Fp8Config, layer: torch.nn.Module):
+        super().__init__(layer.moe_config)
+        self.layer = layer
         self.quant_config = quant_config
         self.block_quant = self.quant_config.weight_block_size is not None
 
-        self.flashinfer_moe_enabled = False
+        self.flashinfer_moe_backend: Optional[FlashinferMoeBackend] = None
+        self.fused_experts: Optional[
+            mk.FusedMoEModularKernel] = None  # type: ignore
         if envs.VLLM_USE_FLASHINFER_MOE_FP8 and has_flashinfer_moe():
+            self.flashinfer_moe_backend = get_flashinfer_moe_backend()
             logger.info_once(
-                "Using FlashInfer MoE FP8 kernels for Fp8MoEMethod.")
-            self.flashinfer_moe_enabled = True
+                f"Using FlashInfer {self.flashinfer_moe_backend.value} kernels"
+            )
         # For GPUs that lack FP8 hardware support, we can leverage the Marlin
         # kernel for fast weight-only FP8 quantization
         self.use_marlin = (not current_platform.has_device_capability(89)
@@ -531,6 +539,20 @@ class Fp8MoEMethod(FusedMoEMethodBase):
                 "CutlassBlockScaledGroupedGemm not supported on the current "
                 "platform.")
 
+    def maybe_make_prepare_finalize(
+        self,
+        moe: FusedMoEConfig,
+    ) -> Optional[mk.FusedMoEPrepareAndFinalize]:
+        if self.flashinfer_moe_backend != FlashinferMoeBackend.CUTLASS:
+            return super().maybe_make_prepare_finalize(moe)
+
+        prepare_finalize = build_flashinfer_fp8_cutlass_moe_prepare_finalize(
+            moe,
+            layer=self.layer,
+        )
+        logger.debug_once("%s", prepare_finalize.__class__.__name__)
+        return prepare_finalize
+
     def create_weights(self, layer: Module, num_experts: int, hidden_size: int,
                        intermediate_size_per_partition: int,
                        params_dtype: torch.dtype, **extra_weight_attrs):
@@ -678,7 +700,7 @@ class Fp8MoEMethod(FusedMoEMethodBase):
                     normalize_e4m3fn_to_e4m3fnuz(
                         layer.w2_weight, layer.w2_weight_scale_inv,
                         layer.w2_input_scale)
-            elif self.flashinfer_moe_enabled:
+            elif self.flashinfer_moe_backend is not None:
                 # NOTE: weights have to be swapped since the activation is
                 # applied on different half for flashinfer vs vllm
                 w13_weight = swap_w13_to_w31(layer.w13_weight.data)
@@ -686,9 +708,6 @@ class Fp8MoEMethod(FusedMoEMethodBase):
                     layer.w13_weight_scale_inv.data)
                 w2_weight = layer.w2_weight.data
                 w2_weight_scale_inv = layer.w2_weight_scale_inv.data
-                if not self.block_quant:
-                    register_moe_scaling_factors(layer)
-                    rotate_flashinfer_fp8_moe_weights(w13_weight, w2_weight)
             else:
                 w13_weight = layer.w13_weight.data
                 w13_weight_scale_inv = layer.w13_weight_scale_inv.data
@@ -834,6 +853,17 @@ class Fp8MoEMethod(FusedMoEMethodBase):
             layer.w13_weight_scale = torch.nn.Parameter(max_w13_scales,
                                                         requires_grad=False)
 
+            if self.flashinfer_moe_backend is not None:
+                # NOTE: weights have to be swapped since the activation is
+                # applied on different half for flashinfer vs vllm
+                assert not self.block_quant
+                register_moe_scaling_factors(layer)
+                w13_weight = swap_w13_to_w31(layer.w13_weight.data)
+                if self.flashinfer_moe_backend == \
+                    FlashinferMoeBackend.TENSORRT_LLM:
+                    rotate_flashinfer_fp8_moe_weights(w13_weight, w2_weight)
+                layer.w13_weight.data = w13_weight.data
+
         if self.use_marlin:
             prepare_moe_fp8_layer_for_marlin(layer, False)
             # Activations not quantized for marlin.
@@ -892,6 +922,13 @@ class Fp8MoEMethod(FusedMoEMethodBase):
                 per_act_token_quant=False,
                 allow_deep_gemm=self.allow_deep_gemm,
             )
+        elif self.flashinfer_moe_backend == FlashinferMoeBackend.CUTLASS:
+            experts = select_cutlass_fp8_gemm_impl(
+                moe,
+                self.layer,
+            )
+            logger.debug_once("Using %s", experts.__class__.__name__)
+            return experts
         else:
             logger.debug(
                 "TritonOrDeepGemmExperts(%s): block_size=%s, per_act_token=%s",
@@ -930,7 +967,48 @@ class Fp8MoEMethod(FusedMoEMethodBase):
             assert logical_to_physical_map is not None
             assert logical_replica_count is not None
             assert isinstance(layer, FusedMoE)
-        if not self.flashinfer_moe_enabled:
+
+        if self.flashinfer_moe_backend == FlashinferMoeBackend.TENSORRT_LLM:
+            assert activation == 'silu', (
+                f"Expected 'silu' activation but got {activation}")
+            assert scoring_func == 'sigmoid', (
+                f"Expected 'sigmoid' scoring func but got {scoring_func}")
+            if self.block_quant:
+                assert (renormalize and use_grouped_topk
+                        and custom_routing_function is None)
+
+                return torch.ops.vllm.flashinfer_fused_moe_blockscale_fp8(
+                    routing_logits=router_logits.to(torch.float32),
+                    routing_bias=e_score_correction_bias,
+                    x=x,
+                    w13_weight=layer.w13_weight,
+                    w13_weight_scale_inv=layer.w13_weight_scale_inv,
+                    w2_weight=layer.w2_weight,
+                    w2_weight_scale_inv=layer.w2_weight_scale_inv,
+                    global_num_experts=global_num_experts,
+                    top_k=top_k,
+                    num_expert_group=num_expert_group,
+                    topk_group=topk_group,
+                    intermediate_size=layer.intermediate_size_per_partition,
+                    expert_offset=layer.ep_rank * layer.local_num_experts,
+                    local_num_experts=layer.local_num_experts,
+                    block_shape=self.quant_config.weight_block_size,
+                    routed_scaling=1.0,
+                )
+            else:
+                assert (not renormalize
+                        and custom_routing_function is not None)
+                return apply_flashinfer_per_tensor_scale_fp8(
+                    layer=layer,
+                    hidden_states=x,
+                    router_logits=router_logits,
+                    routing_bias=e_score_correction_bias,
+                    global_num_experts=global_num_experts,
+                    top_k=top_k,
+                    num_expert_group=num_expert_group,
+                    topk_group=topk_group,
+                    apply_router_weight_on_input=apply_router_weight_on_input)
+
         topk_weights, topk_ids = FusedMoE.select_experts(
             hidden_states=x,
             router_logits=router_logits,
@@ -988,62 +1066,37 @@ class Fp8MoEMethod(FusedMoEMethodBase):
                 apply_router_weight_on_input=apply_router_weight_on_input,
                 global_num_experts=global_num_experts,
                 expert_map=expert_map)
-        elif self.flashinfer_moe_enabled:
-            assert activation == 'silu'
-            assert scoring_func == 'sigmoid'
-            if self.block_quant:
-                assert (renormalize and use_grouped_topk
-                        and custom_routing_function is None)
-
-                return torch.ops.vllm.flashinfer_fused_moe_blockscale_fp8(
-                    routing_logits=router_logits.to(torch.float32),
-                    routing_bias=e_score_correction_bias,
-                    x=x,
-                    w13_weight=layer.w13_weight,
-                    w13_weight_scale_inv=layer.w13_weight_scale_inv,
-                    w2_weight=layer.w2_weight,
-                    w2_weight_scale_inv=layer.w2_weight_scale_inv,
+        elif self.flashinfer_moe_backend == FlashinferMoeBackend.CUTLASS:
+            assert self.block_quant is None
+            assert (not renormalize and custom_routing_function is not None)
+            assert activation == 'silu', (
+                f"Expected 'silu' activation but got {activation}")
+            assert scoring_func == 'sigmoid', (
+                f"Expected 'sigmoid' scoring func but got {scoring_func}")
+            if self.fused_experts is not None:
+                return self.fused_experts(
+                    x,
+                    layer.w13_weight,
+                    layer.w2_weight,
+                    topk_weights,
+                    topk_ids,
+                    inplace=False,
+                    activation=activation,
                     global_num_experts=global_num_experts,
-                    top_k=top_k,
-                    num_expert_group=num_expert_group,
-                    topk_group=topk_group,
-                    intermediate_size=layer.intermediate_size_per_partition,
-                    expert_offset=layer.ep_rank * layer.local_num_experts,
-                    local_num_experts=layer.local_num_experts,
-                    block_shape=self.quant_config.weight_block_size,
-                    routed_scaling=1.0,
+                    expert_map=expert_map,
+                    apply_router_weight_on_input=apply_router_weight_on_input,
                 )
             else:
-                assert (not renormalize
-                        and custom_routing_function is not None)
-                return apply_flashinfer_per_tensor_scale_fp8(
-                    layer=layer,
-                    hidden_states=x,
-                    router_logits=router_logits,
-                    routing_bias=e_score_correction_bias,
-                    global_num_experts=global_num_experts,
-                    top_k=top_k,
-                    num_expert_group=num_expert_group,
-                    topk_group=topk_group,
-                    apply_router_weight_on_input=apply_router_weight_on_input)
-        elif self.fused_experts is not None:
-            return self.fused_experts(
-                hidden_states=x,
-                w1=layer.w13_weight,
-                w2=layer.w2_weight,
-                topk_weights=topk_weights,
-                topk_ids=topk_ids,
-                inplace=True,
+                return flashinfer_cutlass_moe_fp8(
+                    x,
+                    layer,
+                    topk_weights,
+                    topk_ids,
+                    inplace=False,
                     activation=activation,
                     global_num_experts=global_num_experts,
-                apply_router_weight_on_input=apply_router_weight_on_input,
                     expert_map=expert_map,
-                w1_scale=(layer.w13_weight_scale_inv
-                          if self.block_quant else layer.w13_weight_scale),
-                w2_scale=(layer.w2_weight_scale_inv
-                          if self.block_quant else layer.w2_weight_scale),
-                a1_scale=layer.w13_input_scale,
-                a2_scale=layer.w2_input_scale,
+                    apply_router_weight_on_input=apply_router_weight_on_input,
                 )
         else:
             from vllm.model_executor.layers.fused_moe import fused_experts

vllm/model_executor/layers/quantization/modelopt.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
-from enum import Enum
 from typing import Any, Callable, Optional, Union
 
 import torch
@@ -27,8 +26,11 @@ from vllm.model_executor.layers.quantization.utils.flashinfer_fp4_moe import (
     build_flashinfer_fp4_cutlass_moe_prepare_finalize, reorder_w1w3_to_w3w1,
     select_nvfp4_gemm_impl)
 from vllm.model_executor.layers.quantization.utils.flashinfer_utils import (
-    apply_flashinfer_per_tensor_scale_fp8, register_moe_scaling_factors,
-    rotate_flashinfer_fp8_moe_weights, swap_w13_to_w31)
+    FlashinferMoeBackend, apply_flashinfer_per_tensor_scale_fp8,
+    build_flashinfer_fp8_cutlass_moe_prepare_finalize,
+    flashinfer_cutlass_moe_fp8, get_flashinfer_moe_backend,
+    register_moe_scaling_factors, rotate_flashinfer_fp8_moe_weights,
+    select_cutlass_fp8_gemm_impl, swap_w13_to_w31)
 from vllm.model_executor.layers.quantization.utils.marlin_utils_fp4 import (
     apply_fp4_marlin_linear, is_fp4_marlin_supported,
     prepare_fp4_layer_for_marlin, prepare_moe_fp4_layer_for_marlin)
@@ -49,11 +51,6 @@ QUANT_ALGOS = ["FP8", "NVFP4"]
 KV_CACHE_QUANT_ALGOS = ["FP8"]
 
 
-class FlashinferMoeBackend(Enum):
-    TENSORRT_LLM = "TensorRT-LLM"
-    CUTLASS = "CUTLASS"
-
-
 class ModelOptFp8Config(QuantizationConfig):
     """Config class for ModelOpt FP8."""
 
@@ -179,7 +176,7 @@ class ModelOptFp8Config(QuantizationConfig):
         elif isinstance(layer, Attention):
             return ModelOptFp8KVCacheMethod(self)
         elif isinstance(layer, FusedMoE):
-            return ModelOptFp8MoEMethod(self, layer.moe_config)
+            return ModelOptFp8MoEMethod(self, layer)
         return None
 
 
@@ -278,18 +275,49 @@ class ModelOptFp8MoEMethod(FusedMoEMethodBase):
     def __init__(
         self,
         quant_config: ModelOptFp8Config,
-        moe: FusedMoEConfig,
+        layer: torch.nn.Module,
     ) -> None:
-        super().__init__(moe)
+        super().__init__(layer.moe_config)
+        self.layer = layer
         self.quant_config = quant_config
         from vllm.model_executor.layers.quantization.utils.w8a8_utils import (
             cutlass_fp8_supported)
         self.cutlass_fp8_supported = cutlass_fp8_supported()
-        self.flashinfer_moe_enabled = False
+        self.flashinfer_moe_backend: Optional[FlashinferMoeBackend] = None
+        self.fused_experts: Optional[
+            mk.FusedMoEModularKernel] = None  # type: ignore
         if envs.VLLM_USE_FLASHINFER_MOE_FP8 and has_flashinfer_moe():
+            self.flashinfer_moe_backend = get_flashinfer_moe_backend()
             logger.info_once(
-                "Using FlashInfer MoE FP8 kernels for ModelOptFp8MoEMethod.")
-            self.flashinfer_moe_enabled = True
+                f"Using FlashInfer {self.flashinfer_moe_backend.value} kernels"
+            )
+
+    def maybe_make_prepare_finalize(
+        self,
+        moe: FusedMoEConfig,
+    ) -> Optional[mk.FusedMoEPrepareAndFinalize]:
+        if self.fused_experts is not None or \
+            self.flashinfer_moe_backend != FlashinferMoeBackend.CUTLASS:
+            return super().maybe_make_prepare_finalize(moe)
+
+        prepare_finalize = build_flashinfer_fp8_cutlass_moe_prepare_finalize(
+            moe,
+            layer=self.layer,
+        )
+        logger.debug_once("%s", prepare_finalize.__class__.__name__)
+        return prepare_finalize
+
+    def select_gemm_impl(
+        self,
+        prepare_finalize: mk.FusedMoEPrepareAndFinalize,
+        moe: FusedMoEConfig,
+    ) -> mk.FusedMoEPermuteExpertsUnpermute:
+        experts = select_cutlass_fp8_gemm_impl(
+            moe,
+            self.layer,
+        )
+        logger.debug_once("Using %s", experts.__class__.__name__)
+        return experts
 
     def create_weights(
         self,
@@ -433,11 +461,12 @@ class ModelOptFp8MoEMethod(FusedMoEMethodBase):
             layer.w2_input_scale = Parameter(layer.w2_input_scale.max(),
                                              requires_grad=False)
 
-        if self.flashinfer_moe_enabled:
+        if self.flashinfer_moe_backend is not None:
             layer.w13_weight.data = swap_w13_to_w31(layer.w13_weight.data)
+            register_moe_scaling_factors(layer)
+            if self.flashinfer_moe_backend == FlashinferMoeBackend.TENSORRT_LLM:
                 rotate_flashinfer_fp8_moe_weights(layer.w13_weight,
                                                   layer.w2_weight)
-            register_moe_scaling_factors(layer)
 
     def apply(
         self,
@@ -461,14 +490,13 @@ class ModelOptFp8MoEMethod(FusedMoEMethodBase):
         logical_to_physical_map: Optional[torch.Tensor] = None,
         logical_replica_count: Optional[torch.Tensor] = None,
     ) -> torch.Tensor:
-        assert self.fused_experts is None
-
         if enable_eplb:
             raise NotImplementedError(
                 "EPLB not supported for `ModelOptFp8MoEMethod` yet.")
 
-        if self.flashinfer_moe_enabled:
-            assert activation == 'silu'
+        if self.flashinfer_moe_backend == FlashinferMoeBackend.TENSORRT_LLM:
+            assert activation == 'silu', (
+                f"Expected 'silu' activation but got {activation}")
             assert not renormalize
             return apply_flashinfer_per_tensor_scale_fp8(
                 layer=layer,
@@ -495,6 +523,36 @@ class ModelOptFp8MoEMethod(FusedMoEMethodBase):
             e_score_correction_bias=e_score_correction_bias,
             indices_type=self.topk_indices_dtype,
         )
+
+        if self.flashinfer_moe_backend == FlashinferMoeBackend.CUTLASS:
+            assert not renormalize
+            assert activation == 'silu', (
+                f"Expected 'silu' activation but got {activation}")
+            if self.fused_experts is not None:
+                return self.fused_experts(
+                    x,
+                    layer.w13_weight,
+                    layer.w2_weight,
+                    topk_weights,
+                    topk_ids,
+                    inplace=False,
+                    activation=activation,
+                    global_num_experts=global_num_experts,
+                    expert_map=expert_map,
+                    apply_router_weight_on_input=apply_router_weight_on_input,
+                )
+            else:
+                return flashinfer_cutlass_moe_fp8(
+                    x,
+                    layer,
+                    topk_weights,
+                    topk_ids,
+                    inplace=False,
+                    activation=activation,
+                    global_num_experts=global_num_experts,
+                    expert_map=expert_map,
+                    apply_router_weight_on_input=apply_router_weight_on_input,
+                )
         from vllm.model_executor.layers.fused_moe.fused_moe import (
             fused_experts)
         return fused_experts(
@@ -951,20 +1009,10 @@ class ModelOptNvFp4FusedMoE(FusedMoEMethodBase):
         self.flashinfer_moe_backend = None
 
         if self.allow_flashinfer:
-            flashinfer_moe_backend = envs.VLLM_FLASHINFER_MOE_BACKEND
-            if flashinfer_moe_backend == "throughput":
-                self.flashinfer_moe_backend = FlashinferMoeBackend.CUTLASS
-                logger.info_once("Using FlashInfer CUTLASS kernels for "
-                                 "ModelOptNvFp4FusedMoE.")
-            elif flashinfer_moe_backend == "latency":
-                self.flashinfer_moe_backend = FlashinferMoeBackend.TENSORRT_LLM
-                logger.info_once("Using FlashInfer TensorRT-LLM kernels for "
-                                 "ModelOptNvFp4FusedMoE.")
-            else:
-                allowed_backends = ["throughput", "latency"]
-                raise ValueError(
-                    f"Unknown flashinfer moe backend: {flashinfer_moe_backend}"
-                    f" expected one of {allowed_backends}")
+            self.flashinfer_moe_backend = get_flashinfer_moe_backend()
+            logger.info_once(
+                f"Using FlashInfer {self.flashinfer_moe_backend.value} kernels"
+                " for ModelOptNvFp4FusedMoE.")
 
     def maybe_make_prepare_finalize(
         self,

vllm/model_executor/layers/quantization/utils/flashinfer_utils.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+from enum import Enum
 from typing import Optional
 
 import torch
 
+import vllm.model_executor.layers.fused_moe.modular_kernel as mk
+from vllm import envs
+from vllm.logger import init_logger
+from vllm.model_executor.layers.fused_moe.config import FusedMoEConfig
+from vllm.model_executor.layers.fused_moe.flashinfer_cutlass_moe import (
+    FlashInferExperts)
+from vllm.model_executor.layers.fused_moe.flashinfer_cutlass_prepare_finalize import (  # noqa: E501
+    FlashInferCutlassMoEPrepareAndFinalize)
+
+logger = init_logger(__name__)
+
+
+class FlashinferMoeBackend(Enum):
+    TENSORRT_LLM = "TensorRT-LLM"
+    CUTLASS = "CUTLASS"
+
 
 def calculate_tile_tokens_dim(num_tokens, top_k, num_experts):
 
@@ -144,3 +161,98 @@ def register_moe_scaling_factors(layer: torch.nn.Module) -> None:
     layer.register_parameter(
         'output2_scales_scalar',
         torch.nn.Parameter(output2_scales, requires_grad=False))
+    layer.register_parameter(
+        'w2_input_scale_inv',
+        torch.nn.Parameter(1.0 / layer.w2_input_scale, requires_grad=False))
+
+
+def build_flashinfer_fp8_cutlass_moe_prepare_finalize(
+    moe: Optional[FusedMoEConfig],
+    layer: torch.nn.Module,
+) -> mk.FusedMoEPrepareAndFinalize:
+    """Create a FlashInfer CUTLASS fused-MoE prepare finalize kernel"""
+    use_dp = moe.moe_parallel_config.dp_size > 1 if moe is not None else False
+    return FlashInferCutlassMoEPrepareAndFinalize(
+        use_dp, a1_gscale=layer.w13_input_scale)
+
+
+def select_cutlass_fp8_gemm_impl(
+    moe: Optional[FusedMoEConfig],
+    layer: torch.nn.Module,
+    out_dtype: Optional[torch.dtype] = None,
+) -> mk.FusedMoEPermuteExpertsUnpermute:
+    """Return a GEMM *experts* implementation for fused-MoE layers"""
+
+    from vllm.model_executor.models.llama4 import Llama4MoE
+    assert layer.custom_routing_function == Llama4MoE.custom_routing_function, \
+        "FusedMoE flashinfer kernels are only supported for Llama4"
+
+    if moe is not None:
+        return FlashInferExperts(
+            g1_alphas=layer.output1_scales_gate_scalar,
+            g2_alphas=layer.output2_scales_scalar,
+            a1_gscale=layer.w13_input_scale,
+            a2_gscale=layer.w2_input_scale_inv,
+            out_dtype=moe.in_dtype,
+            quant_dtype=torch.float8_e4m3fn,
+            ep_rank=moe.moe_parallel_config.ep_rank,
+            ep_size=moe.moe_parallel_config.ep_size,
+            tp_rank=moe.moe_parallel_config.tp_rank,
+            tp_size=moe.moe_parallel_config.tp_size,
+        )
+
+    assert out_dtype is not None, (
+        "If moe config is None, out_dtype must be passed")
+    return FlashInferExperts(
+        g1_alphas=layer.output1_scales_gate_scalar,
+        g2_alphas=layer.output2_scales_scalar,
+        a1_gscale=layer.w13_input_scale,
+        a2_gscale=layer.w2_input_scale_inv,
+        out_dtype=out_dtype,
+        quant_dtype=torch.float8_e4m3fn,
+    )
+
+
+def flashinfer_cutlass_moe_fp8(
+    hidden_states: torch.Tensor,
+    layer: torch.nn.Module,
+    topk_weights: torch.Tensor,
+    topk_ids: torch.Tensor,
+    inplace: bool = False,
+    activation: str = "silu",
+    global_num_experts: int = -1,
+    expert_map: Optional[torch.Tensor] = None,
+    apply_router_weight_on_input: bool = False,
+) -> torch.Tensor:
+    fused_experts = mk.FusedMoEModularKernel(
+        build_flashinfer_fp8_cutlass_moe_prepare_finalize(moe=None,
+                                                          layer=layer),
+        select_cutlass_fp8_gemm_impl(moe=None,
+                                     layer=layer,
+                                     out_dtype=hidden_states.dtype))
+
+    return fused_experts(
+        hidden_states,
+        layer.w13_weight,
+        layer.w2_weight,
+        topk_weights,
+        topk_ids,
+        inplace=inplace,
+        activation=activation,
+        global_num_experts=global_num_experts,
+        expert_map=expert_map,
+        apply_router_weight_on_input=apply_router_weight_on_input,
+    )
+
+
+def get_flashinfer_moe_backend() -> FlashinferMoeBackend:
+    flashinfer_moe_backend = envs.VLLM_FLASHINFER_MOE_BACKEND
+    if flashinfer_moe_backend == "throughput":
+        return FlashinferMoeBackend.CUTLASS
+    elif flashinfer_moe_backend == "latency":
+        return FlashinferMoeBackend.TENSORRT_LLM
+
+    allowed_backends = ["throughput", "latency"]
+    raise ValueError(
+        f"Unknown flashinfer moe backend: {flashinfer_moe_backend}"
+        f" expected one of {allowed_backends}")