[BugFix] Fix LoRA Fp8 (#33879)

Signed-off-by: Daniel Serebrenik <daserebrenik@nvidia.com>

vllm/lora/layers/fused_moe.py

@@ -130,6 +130,11 @@ class FusedMoEWithLoRA(BaseLayerWithLoRA):
         self.base_layer.ensure_moe_quant_config_init()
         quant_config = self.base_layer.quant_method.moe_quant_config
 
+        if getattr(self.base_layer.quant_method, "supports_internal_mk", False):
+            # Use the existing modular kernel from the quant method
+            m_fused_moe_fn = self.base_layer.quant_method.moe_mk
+        else:
+            # Create a new modular kernel via select_gemm_impl
             prepare_finalize = MoEPrepareAndFinalizeNoEP()
             m_fused_moe_fn = FusedMoEModularKernel(
                 prepare_finalize,
@@ -138,6 +143,7 @@ class FusedMoEWithLoRA(BaseLayerWithLoRA):
                 ),
                 self.base_layer.shared_experts,
             )
+
         if quant_config.use_mxfp4_w4a16:
             assert isinstance(
                 m_fused_moe_fn.fused_experts, (MarlinExperts, UnfusedOAITritonExperts)