[Perf] Trim HunyuanVideo encoder padding tokens (#3844)

Signed-off-by: david6666666 <530634352@qq.com>
Co-authored-by: SYLAR <125541396+lishunyang12@users.noreply.github.com>

vllm_omni/diffusion/models/hunyuan_video/hunyuan_video_15_transformer.py

@@ -764,6 +764,13 @@ class HunyuanVideo15Transformer3DModel(nn.Module):
 
         # Create explicit attn_mask for image tokens when SP auto_pad is active.
         ctx = get_forward_context()
+        if not ctx.sp_active:
+            max_valid_encoder_tokens = int(encoder_attention_mask.sum(dim=1).max().item())
+            if max_valid_encoder_tokens < encoder_attention_mask.shape[1]:
+                encoder_hidden_states = encoder_hidden_states[:, :max_valid_encoder_tokens]
+                encoder_attention_mask = encoder_attention_mask[:, :max_valid_encoder_tokens]
+            if encoder_attention_mask.all():
+                encoder_attention_mask = None
         hidden_states_mask = None
         if ctx.sp_original_seq_len is not None and ctx.sp_padding_size > 0:
             padded_seq_len = ctx.sp_original_seq_len + ctx.sp_padding_size