[PERF] Remove TRTLLM Gen attn kernel limitation `max_seq_len <=131072` (#28755)

Signed-off-by: Vadim Gimpelson <vadim.gimpelson@gmail.com>

vllm/config/vllm.py

@@ -483,21 +483,6 @@ class VllmConfig:
                             "Overriding cudagraph_mode to PIECEWISE."
                         )
                         self.compilation_config.cudagraph_mode = CUDAGraphMode.PIECEWISE
-                    elif (
-                        current_platform.is_cuda()
-                        and current_platform.is_device_capability(100)
-                        and self.model_config.max_model_len > 131072
-                        and not self.model_config.use_mla
-                    ):
-                        # Refer to vllm/utils/flashinfer.py::use_trtllm_attention()
-                        logger.warning_once(
-                            "NVIDIA Blackwell TRTLLM attention cannot support "
-                            "max_model_len >= 131072 (found "
-                            f"{self.model_config.max_model_len}), causing dynamic "
-                            "dispatching that breaks full cudagraphs. "
-                            "Overriding cudagraph_mode to PIECEWISE."
-                        )
-                        self.compilation_config.cudagraph_mode = CUDAGraphMode.PIECEWISE
 
             # disable cudagraph when enforce eager execution
             if self.model_config is not None and self.model_config.enforce_eager:

vllm/utils/flashinfer.py

@@ -319,14 +319,12 @@ def use_trtllm_attention(
         # Environment variable not set - use auto-detection
         if is_prefill:
             # Prefill auto-detection
-            use_trtllm = max_seq_len <= 131072 and kv_cache_dtype == "auto"
+            use_trtllm = kv_cache_dtype == "auto"
             if use_trtllm:
                 logger.warning_once("Using TRTLLM prefill attention (auto-detected).")
         else:
             # Decode auto-detection
-            use_trtllm = (
-                num_tokens <= 256 and max_seq_len <= 131072 and kv_cache_dtype == "auto"
-            )
+            use_trtllm = num_tokens <= 256 and kv_cache_dtype == "auto"
             if use_trtllm:
                 logger.warning_once("Using TRTLLM decode attention (auto-detected).")
         return use_trtllm