[V1] Update interface for mistral-format Pixtral (#10703)

Signed-off-by: Roger Wang <ywang@roblox.com>

vllm/model_executor/models/pixtral.py

@@ -31,7 +31,7 @@ from vllm.model_executor.model_loader.weight_utils import default_weight_loader
 from vllm.model_executor.models.utils import merge_multimodal_embeddings
 from vllm.model_executor.sampling_metadata import SamplingMetadata
 from vllm.multimodal import MULTIMODAL_REGISTRY, MultiModalKwargs
-from vllm.multimodal.inputs import PlaceholderRange
+from vllm.multimodal.inputs import NestedTensors, PlaceholderRange
 from vllm.multimodal.utils import (cached_get_tokenizer,
                                    consecutive_placeholder_ranges,
                                    resolve_visual_encoder_outputs)
@@ -190,6 +190,25 @@ class PixtralForConditionalGeneration(nn.Module, SupportsMultiModal,
 
         return get_sampler()
 
+    def get_multimodal_embeddings(self, **kwargs) -> Optional[NestedTensors]:
+        image_input = self._parse_and_validate_image_input(**kwargs)
+        if image_input is None:
+            return None
+        vision_embeddings = self._process_image_input(image_input)
+        return vision_embeddings
+
+    def get_input_embeddings(
+        self,
+        input_ids: torch.Tensor,
+        multimodal_embeddings: Optional[NestedTensors] = None,
+    ) -> torch.Tensor:
+        inputs_embeds = self.language_model.get_input_embeddings(input_ids)
+        if multimodal_embeddings is not None:
+            inputs_embeds = merge_multimodal_embeddings(
+                input_ids, inputs_embeds, multimodal_embeddings,
+                self.vision_args.image_token_id)
+        return inputs_embeds
+
     def forward(
         self,
         input_ids: torch.Tensor,
@@ -197,31 +216,21 @@ class PixtralForConditionalGeneration(nn.Module, SupportsMultiModal,
         kv_caches: List[torch.Tensor],
         attn_metadata: AttentionMetadata,
         intermediate_tensors: Optional[IntermediateTensors] = None,
+        inputs_embeds: Optional[torch.Tensor] = None,
         **kwargs: object,
     ) -> Union[torch.Tensor, IntermediateTensors]:
         """Run forward pass for pixtral.
-
-        TODO
-
         """
         if intermediate_tensors is not None:
-            input_ids = None
             inputs_embeds = None
-        else:
-            image_input = self._parse_and_validate_image_input(**kwargs)
-
-            if image_input is not None:
-                vision_embeddings = self._process_image_input(image_input)
-                inputs_embeds = self.language_model.model.get_input_embeddings(
-                    input_ids)
 
-                inputs_embeds = merge_multimodal_embeddings(
-                    input_ids, inputs_embeds, vision_embeddings,
-                    self.vision_args.image_token_id)
-
-                input_ids = None
-            else:
-                inputs_embeds = None
+        # NOTE: In v1, inputs_embeds is always generated at model runner, this
+        # condition is for v0 compatibility.
+        elif inputs_embeds is None:
+            vision_embeddings = self.get_multimodal_embeddings(**kwargs)
+            inputs_embeds = self.get_input_embeddings(input_ids,
+                                                      vision_embeddings)
+            input_ids = None
 
         hidden_states = self.language_model.model(input_ids,
                                                   positions,