[Bugfix] Revert custom attention mask for gemma3-mm (#28995)

Signed-off-by: Isotr0py <mozf@mail2.sysu.edu.cn>
Co-authored-by: Cyrus Leung <tlleungac@connect.ust.hk>

Author: Isotr0py

vllm/config/model.py

@@ -32,7 +32,6 @@
     try_get_generation_config,
     try_get_safetensors_metadata,
     try_get_tokenizer_config,
-    uses_custom_attention_masks,
     uses_mrope,
 )
 from vllm.transformers_utils.gguf_utils import (
@@ -1625,10 +1624,6 @@ def uses_alibi(self) -> bool:
     def uses_mrope(self) -> bool:
         return uses_mrope(self.hf_config)
 
-    @property
-    def uses_custom_attention_masks(self) -> bool:
-        return uses_custom_attention_masks(self.hf_config)
-
     @property
     def is_multimodal_model(self) -> bool:
         return self.multimodal_config is not None

vllm/model_executor/models/gemma3_mm.py

@@ -596,7 +596,7 @@ def _process_image_input(
     def get_language_model(self) -> torch.nn.Module:
         return self.language_model
 
-    def get_multimodal_embeddings(self, **kwargs: object) -> MultiModalEmbeddings:
+    def embed_multimodal(self, **kwargs: object) -> MultiModalEmbeddings:
         image_input = self._parse_and_validate_image_input(**kwargs)
         if image_input is None:
             return []
@@ -644,142 +644,6 @@ def forward(
 
         return hidden_states
 
-    def generate_attention_masks(
-        self,
-        input_ids: torch.Tensor,
-        positions: torch.Tensor,
-        mask_dtype: torch.dtype,
-    ) -> dict[str, Any]:
-        """Generate custom attention masks for Gemma3 multimodal inputs.
-
-        This is called by V1 engine's gpu_model_runner during preprocessing
-        to generate attention masks that allow bidirectional attention between
-        image tokens while maintaining causal attention for text.
-        """
-        # NOTE(woosuk): Here, we distinguish the sequences by the position id 0.
-        # This is a HACK. Fix this.
-        start_indices = (positions == 0).cpu().nonzero()
-        num_seqs = len(start_indices)
-        seq_lens = []
-        for i in range(num_seqs):
-            start_idx = start_indices[i]
-            end_idx = start_indices[i + 1] if i < num_seqs - 1 else len(input_ids)
-            seq_lens.append(end_idx - start_idx)
-
-        global_attn_masks = []
-        local_attn_masks = []
-        start_idx = 0
-        for seq_idx, seq_len in enumerate(seq_lens):
-            end_idx = start_idx + seq_len
-            input_token_ids = input_ids[start_idx:end_idx]
-
-            # Find image token positions
-            img_pos = input_token_ids == self.config.image_token_index
-
-            start_idx = end_idx
-
-            # Create a global causal mask
-            global_attn_mask = torch.empty(
-                1,
-                1,
-                seq_len,
-                seq_len,
-                dtype=mask_dtype,
-                device=input_ids.device,
-            )
-            global_attn_mask.fill_(float("-inf"))
-            # Fill the lower triangle with 0 (causal attention)
-            global_attn_mask = global_attn_mask.triu(diagonal=1)
-
-            # Enable bidirectional attention between image tokens
-            img_mask = torch.zeros_like(global_attn_mask)
-            img_mask[:, :, :, img_pos] += 1
-            img_mask[:, :, img_pos, :] += 1
-            global_attn_mask = torch.where(img_mask == 2, 0, global_attn_mask)
-            global_attn_masks.append(global_attn_mask)
-
-            # GGUF compatibility: config might be Gemma3TextConfig directly
-            text_config = getattr(self.config, "text_config", self.config)
-            sliding_window = text_config.sliding_window
-            if sliding_window is not None:
-                # Create a local causal mask with sliding window (1024)
-                local_attn_mask = torch.ones_like(global_attn_mask)
-                local_attn_mask = torch.tril(local_attn_mask, diagonal=-sliding_window)
-                local_attn_mask = torch.where(
-                    local_attn_mask == 0, global_attn_mask, float("-inf")
-                )
-                local_attn_masks.append(local_attn_mask)
-
-        return {
-            "has_images": True,
-            "seq_lens": seq_lens,
-            "global_attn_masks": global_attn_masks,
-            "local_attn_masks": local_attn_masks,
-        }
-
-    def prepare_attn_masks(
-        self,
-        input_ids: torch.Tensor,
-        positions: torch.Tensor,
-        mask_dtype: torch.dtype,
-        **kwargs,
-    ):
-        kwargs["has_images"] = True
-        # NOTE(woosuk): Here, we distinguish the sequences by the position id 0.
-        # This is a HACK. Fix this.
-        start_indices = (positions == 0).cpu().nonzero()
-        num_seqs = len(start_indices)
-        seq_lens = []
-        for i in range(num_seqs):
-            start_idx = start_indices[i].item()
-            if i < num_seqs - 1:
-                end_idx = start_indices[i + 1].item()
-            else:
-                end_idx = len(input_ids)
-            seq_lens.append(end_idx - start_idx)
-        kwargs["seq_lens"] = seq_lens
-
-        global_attn_masks = []
-        local_attn_masks = []
-        start_idx = 0
-        for seq_len in seq_lens:
-            end_idx = start_idx + seq_len
-            input_token_ids = input_ids[start_idx:end_idx]
-            start_idx = end_idx
-            # Create a global causal mask.
-            global_attn_mask = torch.empty(
-                1,
-                1,
-                seq_len,
-                seq_len,
-                dtype=mask_dtype,
-                device=input_ids.device,
-            )
-            global_attn_mask.fill_(float("-inf"))
-            # Fill the lower triangle with 0.
-            global_attn_mask = global_attn_mask.triu(diagonal=1)
-
-            # Consider the bidirectional attention between image tokens.
-            img_mask = torch.zeros_like(global_attn_mask)
-            img_pos = input_token_ids == self.config.image_token_index
-            img_mask[:, :, :, img_pos] += 1
-            img_mask[:, :, img_pos, :] += 1
-            global_attn_mask = torch.where(img_mask == 2, 0, global_attn_mask)
-            global_attn_masks.append(global_attn_mask)
-
-            sliding_window = self.config.text_config.sliding_window
-            if sliding_window is not None:
-                # Create a local causal mask with sliding window (1024).
-                local_attn_mask = torch.ones_like(global_attn_mask)
-                local_attn_mask = torch.tril(local_attn_mask, diagonal=-sliding_window)
-                local_attn_mask = torch.where(
-                    local_attn_mask == 0, global_attn_mask, float("-inf")
-                )
-                local_attn_masks.append(local_attn_mask)
-        kwargs["global_attn_masks"] = global_attn_masks
-        kwargs["local_attn_masks"] = local_attn_masks
-        return kwargs
-
     def compute_logits(
         self,
         hidden_states: torch.Tensor,

vllm/transformers_utils/config.py

@@ -520,17 +520,6 @@ def is_interleaved(config: PretrainedConfig) -> bool:
     return False
 
 
-def uses_custom_attention_masks(config: PretrainedConfig) -> bool:
-    """Detect if model uses custom attention mask generation for multimodal.
-
-    Some multimodal models require custom attention masks that enable
-    bidirectional attention between image tokens while maintaining causal
-    attention for text tokens. Currently applies to Gemma3 multimodal models.
-    """
-    architectures = getattr(config, "architectures", [])
-    return "Gemma3ForConditionalGeneration" in architectures
-
-
 def _maybe_update_auto_config_kwargs(kwargs: dict[str, Any], model_type: str):
     """
     Update kwargs for AutoConfig initialization based on model_type

vllm/v1/worker/gpu_model_runner.py

@@ -324,7 +324,6 @@ def __init__(
         # Multi-modal data support
         self.mm_registry = MULTIMODAL_REGISTRY
         self.uses_mrope = model_config.uses_mrope
-        self.uses_custom_attention_masks = model_config.uses_custom_attention_masks
         self.supports_mm_inputs = self.mm_registry.supports_multimodal_inputs(
             model_config
         )
@@ -2352,24 +2351,6 @@ def _preprocess(
                 **self._init_model_kwargs(num_scheduled_tokens),
                 **self._extract_mm_kwargs(scheduler_output),
             }
-
-            # Generate custom attention masks for models that require them.
-            # V1 pre-generates embeddings, so forward() skips prepare_attn_masks().
-            # Check mm_features (mm_embeds is empty during decode).
-            has_mm_features = any(
-                req_state.mm_features for req_state in self.requests.values()
-            )
-            if (
-                self.uses_custom_attention_masks
-                and has_mm_features
-                and hasattr(self.model, "generate_attention_masks")
-            ):
-                mask_kwargs = self.model.generate_attention_masks(
-                    self.input_ids.gpu[:num_scheduled_tokens],
-                    self.positions.gpu[:num_scheduled_tokens],
-                    mask_dtype=self.model.dtype,
-                )
-                model_kwargs.update(mask_kwargs)
         elif self.enable_prompt_embeds and is_first_rank:
             # Get the input embeddings for the tokens that are not input embeds,
             # then put them into the appropriate positions.