Enable gpt-oss mxfp4 on older hardware (sm75+) (#39940)

Co-authored-by: Marc Sun <57196510+SunMarc@users.noreply.github.com>

src/transformers/integrations/mxfp4.py

@@ -280,7 +280,10 @@ def mlp_forward(self, hidden_states):
     batch_size = hidden_states.shape[0]
     hidden_states = hidden_states.reshape(-1, self.router.hidden_dim)
     router_logits = nn.functional.linear(hidden_states, self.router.weight, self.router.bias)
-    routing_data, gather_idx, scatter_idx = routing(router_logits, self.router.top_k)
+
+    with torch.cuda.device(router_logits.device):
+        routing_data, gather_idx, scatter_idx = routing(router_logits, self.router.top_k)
+
     routed_out = self.experts(hidden_states, routing_data, gather_idx, scatter_idx)
     routed_out = routed_out.reshape(batch_size, -1, self.router.hidden_dim)
     return routed_out, router_logits

src/transformers/quantizers/quantizer_mxfp4.py

@@ -67,23 +67,33 @@ class Mxfp4HfQuantizer(HfQuantizer):
             raise ImportError("Using mxfp4 requires Accelerate: `pip install accelerate`")
 
         compute_capability = torch.cuda.get_device_capability()
-        major, minor = compute_capability
+        gpu_is_supported = compute_capability >= (7, 5)
+        kernels_available = is_triton_available("3.4.0") and is_triton_kernels_availalble()
 
-        if not is_triton_available("3.4.0") or not is_triton_kernels_availalble():
-            if self.pre_quantized and not self.quantization_config.dequantize:
+        if self.pre_quantized:
+            # On unsupported GPUs or without kernels, we will dequantize the model to bf16
+            if not gpu_is_supported:
+                logger.warning_once(
+                    "MXFP4 quantization is only supported on GPUs with compute capability >= 7.5 (e.g T4, A100, L4, H100, or B200). "
+                    "We will default to dequantizing the model to bf16."
+                )
+                self.quantization_config.dequantize = True
+                return
+
+            if not kernels_available:
                 logger.warning_once(
                     "MXFP4 quantization requires triton >= 3.4.0 and triton_kernels installed, we will default to dequantizing the model to bf16"
                 )
                 self.quantization_config.dequantize = True
                 return
-            else:
-                # we can't quantize the model in this case so we raise an error
-                raise ValueError("MXFP4 quantization requires triton >= 3.4.0 and triton_kernels installed")
-
-        if major < 9:
+        elif not gpu_is_supported:
+            # we can't quantize the model in this case so we raise an error
             raise ValueError(
-                "MXFP4 quantized models is only supported on GPUs with compute capability >= 9.0 (e.g H100, or B100)"
+                "MXFP4 quantization is only supported on GPUs with compute capability >= 7.5 (e.g T4, A100, L4, H100, or B200)"
             )
+        elif not kernels_available:
+            # we can't quantize the model in this case so we raise an error
+            raise ValueError("MXFP4 quantization requires triton >= 3.4.0 and triton_kernels installed")
 
         device_map = kwargs.get("device_map", None)
         if device_map is None:

tests/quantization/mxfp4/test_mxfp4.py

@@ -107,18 +107,31 @@ class Mxfp4QuantizerTest(unittest.TestCase):
 
     def test_quantizer_validation_low_compute_capability(self):
         """Test quantizer validation with low compute capability"""
-        with patch("torch.cuda.get_device_capability", return_value=(8, 0)):
+        with patch("torch.cuda.get_device_capability", return_value=(7, 0)):
+            from transformers.quantizers.quantizer_mxfp4 import Mxfp4HfQuantizer
+
+            config = Mxfp4Config()
+            quantizer = Mxfp4HfQuantizer(config)
+            quantizer.pre_quantized = False
+
+            with self.assertRaises(ValueError):
+                quantizer.validate_environment()
+
+    def test_quantizer_validation_low_compute_capability_with_prequantized(self):
+        """Test quantizer validation with low compute capability"""
+        with patch("torch.cuda.get_device_capability", return_value=(7, 0)):
             from transformers.quantizers.quantizer_mxfp4 import Mxfp4HfQuantizer
 
             config = Mxfp4Config()
             quantizer = Mxfp4HfQuantizer(config)
 
-            with self.assertRaises(ValueError):
-                quantizer.validate_environment()
+            # Should automatically set dequantize=True and warn
+            quantizer.validate_environment()
+            self.assertTrue(quantizer.quantization_config.dequantize)
 
     def test_quantizer_validation_low_compute_capability_with_dequantize(self):
         """Test quantizer validation with low compute capability but dequantize enabled"""
-        with patch("torch.cuda.get_device_capability", return_value=(8, 0)):
+        with patch("torch.cuda.get_device_capability", return_value=(7, 0)):
             from transformers.quantizers.quantizer_mxfp4 import Mxfp4HfQuantizer
 
             config = Mxfp4Config(dequantize=True)