[BugFix] Correct max_model_len derivation from config.json for Mistral format (#17937)

Signed-off-by: 汪志鹏 <wangzhipeng628@gmail.com>
Co-authored-by: tracelogfb <48808670+tracelogfb@users.noreply.github.com>
Co-authored-by: Stephen Chen <tracelog@meta.com>

vllm/transformers_utils/config.py

@@ -686,9 +686,24 @@ def load_params_config(model: Union[str, Path], revision: Optional[str],
     config_dict["hidden_act"] = config_dict.get("activation", "silu")
     config_dict["tie_word_embeddings"] = config_dict.get(
         "tie_embeddings", False)
-    config_dict["max_seq_len"] = config_dict.get("max_seq_len", 128_000)
-    config_dict["max_position_embeddings"] = config_dict.get(
-        "max_position_embeddings", 128_000)
+
+    if config_dict.get("max_position_embeddings") is None:
+        max_position_embeddings = 128_000
+        try:
+            trust_remote_code_val = kwargs.get("trust_remote_code", False)
+            hf_config = get_config(model=model,
+                                   trust_remote_code=trust_remote_code_val,
+                                   revision=revision,
+                                   config_format=ConfigFormat.HF)
+            if hf_value := hf_config.get_text_config().max_position_embeddings:
+                max_position_embeddings = hf_value
+        except Exception as e:
+            logger.warning(
+                "The params.json file is missing 'max_position_embeddings'"
+                " and could not get a value from the HF config."
+                " Defaulting to 128000",
+                exc_info=e)
+        config_dict["max_position_embeddings"] = max_position_embeddings
 
     if config_dict.get("quantization") is not None:
         quantization = config_dict.get("quantization", {})