[Misc] Qwen MoE model supports LoRA (#20932)

Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>

Author: jeejeelee

docs/models/supported_models.md

@@ -380,9 +380,9 @@ Specified using `--task generate`.
 | `Plamo2ForCausalLM` | PLaMo2 | `pfnet/plamo-2-1b`, `pfnet/plamo-2-8b`, etc. | | | |
 | `QWenLMHeadModel` | Qwen | `Qwen/Qwen-7B`, `Qwen/Qwen-7B-Chat`, etc. | ✅︎ | ✅︎ | ✅︎ |
 | `Qwen2ForCausalLM` | QwQ, Qwen2 | `Qwen/QwQ-32B-Preview`, `Qwen/Qwen2-7B-Instruct`, `Qwen/Qwen2-7B`, etc. | ✅︎ | ✅︎ | ✅︎ |
-| `Qwen2MoeForCausalLM` | Qwen2MoE | `Qwen/Qwen1.5-MoE-A2.7B`, `Qwen/Qwen1.5-MoE-A2.7B-Chat`, etc. | | ✅︎ | ✅︎ |
+| `Qwen2MoeForCausalLM` | Qwen2MoE | `Qwen/Qwen1.5-MoE-A2.7B`, `Qwen/Qwen1.5-MoE-A2.7B-Chat`, etc. | ✅︎ | ✅︎ | ✅︎ |
 | `Qwen3ForCausalLM` | Qwen3 | `Qwen/Qwen3-8B`, etc. | ✅︎ | ✅︎ | ✅︎ |
-| `Qwen3MoeForCausalLM` | Qwen3MoE | `Qwen/Qwen3-30B-A3B`, etc. | | ✅︎ | ✅︎ |
+| `Qwen3MoeForCausalLM` | Qwen3MoE | `Qwen/Qwen3-30B-A3B`, etc. | ✅︎ | ✅︎ | ✅︎ |
 | `StableLmForCausalLM` | StableLM | `stabilityai/stablelm-3b-4e1t`, `stabilityai/stablelm-base-alpha-7b-v2`, etc. | | | ✅︎ |
 | `Starcoder2ForCausalLM` | Starcoder2 | `bigcode/starcoder2-3b`, `bigcode/starcoder2-7b`, `bigcode/starcoder2-15b`, etc. | | ✅︎ | ✅︎ |
 | `SolarForCausalLM` | Solar Pro | `upstage/solar-pro-preview-instruct`, etc. | ✅︎ | ✅︎ | ✅︎ |

vllm/lora/models.py

@@ -29,6 +29,7 @@
                              get_supported_lora_modules,
                              is_regex_target_modules,
                              parse_fine_tuned_lora_name, replace_submodule)
+from vllm.model_executor.layers.fused_moe import FusedMoE
 from vllm.model_executor.model_loader.tensorizer import TensorizerConfig
 from vllm.model_executor.models import SupportsLoRA, supports_multimodal
 from vllm.model_executor.models.interfaces import is_pooling_model
@@ -60,6 +61,17 @@ def get_lora_id():
     return _GLOBAL_LORA_ID
 
 
+def is_moe_model(model: nn.Module) -> bool:
+    """Checks if the model contains FusedMoE layers and warns the user."""
+    if any(isinstance(module, FusedMoE) for module in model.modules()):
+        logger.warning_once(
+            "For MoE models, vLLM currently does not support fused MoE LoRA "
+            "inference. Please ensure that the loaded LoRA model does not "
+            "contain expert weights.")
+        return True
+    return False
+
+
 class LoRAModel(AdapterModel):
     """A LoRA fine-tuned model."""
 
@@ -375,6 +387,7 @@ def __init__(
             # text modules (e.g. ChatGLM)
             and hasattr(self.model, "get_mm_mapping"))
         self.is_pooling_model = is_pooling_model(self.model)
+        self.is_moe_model = is_moe_model(self.model)
         self.packed_modules: dict[str, list[str]] = {}
         self.modules: dict[str, BaseLayerWithLoRA] = {}
         # Dict instead of a set for compatibility with LRUCache.

vllm/model_executor/models/qwen2_moe.py

@@ -53,7 +53,7 @@
 from vllm.model_executor.sampling_metadata import SamplingMetadata
 from vllm.sequence import IntermediateTensors
 
-from .interfaces import SupportsPP
+from .interfaces import SupportsLoRA, SupportsPP
 from .utils import (AutoWeightsLoader, extract_layer_index,
                     is_pp_missing_parameter,
                     make_empty_intermediate_tensors_factory, make_layers,
@@ -448,8 +448,7 @@ def load_weights(self, weights: Iterable[tuple[str,
                     if weight_name not in name:
                         continue
                     name = name.replace(weight_name, param_name)
-                    if "layers.13.mlp.experts.w2_weight" in name:
-                        pass
+
                     # Skip layers on other devices.
                     if is_pp_missing_parameter(name, self):
                         continue
@@ -494,7 +493,7 @@ def load_weights(self, weights: Iterable[tuple[str,
         return loaded_params
 
 
-class Qwen2MoeForCausalLM(nn.Module, SupportsPP):
+class Qwen2MoeForCausalLM(nn.Module, SupportsPP, SupportsLoRA):
 
     fall_back_to_pt_during_load = False
     packed_modules_mapping = {

vllm/model_executor/models/qwen3_moe.py

@@ -50,7 +50,7 @@
 from vllm.model_executor.sampling_metadata import SamplingMetadata
 from vllm.sequence import IntermediateTensors
 
-from .interfaces import SupportsPP
+from .interfaces import SupportsLoRA, SupportsPP
 from .utils import (AutoWeightsLoader, extract_layer_index,
                     is_pp_missing_parameter,
                     make_empty_intermediate_tensors_factory, make_layers,
@@ -482,7 +482,7 @@ def load_weights(self, weights: Iterable[tuple[str,
         return loaded_params
 
 
-class Qwen3MoeForCausalLM(nn.Module, SupportsPP):
+class Qwen3MoeForCausalLM(nn.Module, SupportsPP, SupportsLoRA):
     packed_modules_mapping = {
         "qkv_proj": [
             "q_proj",