[Misc] Fix seq_lens for graph capture (vllm-project#23175)

Signed-off-by: Woosuk Kwon <[email protected]>

Author: WoosukKwon

vllm/v1/worker/gpu_model_runner.py

@@ -2317,15 +2317,13 @@ def _dummy_run(
 
         # If force_attention is True, we always capture attention. Otherwise,
         # it only happens for cudagraph_runtime_mode=FULL.
-        if force_attention or cudagraph_runtime_mode == \
-                CUDAGraphMode.FULL:
+        if force_attention or cudagraph_runtime_mode == CUDAGraphMode.FULL:
             attn_metadata = {}
 
             # Make sure max_model_len is used at the graph capture time.
             self.seq_lens_np[:num_reqs] = self.max_model_len
             self.seq_lens_np[num_reqs:] = 0
-            self.seq_lens[:num_reqs].copy_(self.seq_lens_cpu[:num_reqs],
-                                           non_blocking=True)
+            self.seq_lens.copy_(self.seq_lens_cpu, non_blocking=True)
 
             for kv_cache_group_id, kv_cache_group_spec in enumerate(
                     self.kv_cache_config.kv_cache_groups):