bugfix: bug fix on determine_attention_backend condition (#688)

Should only enable fa3 for cuda 12.3+

flashinfer/utils.py

@@ -20,6 +20,7 @@
 from typing import Callable, Dict, Iterable, Optional, Sequence, Tuple, Union
 
 import torch
+import torch.version
 from torch.torch_version import TorchVersion
 from torch.torch_version import __version__ as torch_version
 
@@ -342,12 +343,16 @@ def determine_attention_backend(
     """
     major, _ = get_compute_capability(device)
 
-    if major >= 9 and is_fa3_backend_supported(
-        pos_encoding_mode,
-        allow_fp16_qk_reductions,
-        use_custom_mask,
-        dtype_q,
-        dtype_kv,
+    if (
+        major >= 9
+        and torch.version.cuda >= "12.3"
+        and is_fa3_backend_supported(
+            pos_encoding_mode,
+            allow_fp16_qk_reductions,
+            use_custom_mask,
+            dtype_q,
+            dtype_kv,
+        )
     ):
         return "fa3"
     else: