[Bugfix] Fix the CUDA version check for FP8 support in the CUTLASS kernels (vllm-project#5715)

Author: tlrmchlsmth

csrc/ops.h

@@ -92,6 +92,8 @@ torch::Tensor gptq_marlin_repack(torch::Tensor& b_q_weight, torch::Tensor& perm,
                                  int64_t size_k, int64_t size_n,
                                  int64_t num_bits);
 
+bool cutlass_scaled_mm_supports_fp8(int64_t cuda_device_capability);
+
 void cutlass_scaled_mm(torch::Tensor& out, torch::Tensor const& a,
                        torch::Tensor const& b, torch::Tensor const& a_scales,
                        torch::Tensor const& b_scales);

csrc/quantization/cutlass_w8a8/scaled_mm_entry.cu

@@ -25,6 +25,22 @@ void cutlass_scaled_mm_sm90(torch::Tensor& c, torch::Tensor const& a,
                             torch::Tensor const& b_scales);
 #endif
 
+bool cutlass_scaled_mm_supports_fp8(int64_t cuda_device_capability) {
+  // CUTLASS FP8 kernels need at least
+  //   CUDA 12.0 on SM90 systems (Hopper)
+  //   CUDA 12.4 on SM89 systems (Lovelace)
+
+#if defined CUDA_VERSION
+  if (cuda_device_capability >= 90) {
+    return CUDA_VERSION >= 12000;
+  } else if (cuda_device_capability >= 89) {
+    return CUDA_VERSION >= 12040;
+  }
+#endif
+
+  return false;
+}
+
 void cutlass_scaled_mm(torch::Tensor& c, torch::Tensor const& a,
                        torch::Tensor const& b, torch::Tensor const& a_scales,
                        torch::Tensor const& b_scales) {

csrc/torch_bindings.cpp

@@ -144,6 +144,12 @@ TORCH_LIBRARY_EXPAND(TORCH_EXTENSION_NAME, ops) {
       "                  Tensor b, Tensor a_scales,"
       "                  Tensor b_scales) -> ()");
   ops.impl("cutlass_scaled_mm", torch::kCUDA, &cutlass_scaled_mm);
+
+  // Check if cutlass scaled_mm is supported for CUDA devices of the given
+  // capability
+  ops.def("cutlass_scaled_mm_supports_fp8", &cutlass_scaled_mm_supports_fp8);
+  ops.impl("cutlass_scaled_mm_supports_fp8", torch::kCUDA,
+           &cutlass_scaled_mm_supports_fp8);
 #endif
 
   // Quantized GEMM for GPTQ.

vllm/_custom_ops.py

@@ -216,6 +216,10 @@ def gptq_marlin_24_gemm(a: torch.Tensor, b_q_weight: torch.Tensor,
 
 
 # cutlass
+def cutlass_scaled_mm_supports_fp8(cuda_device_capability: int) -> bool:
+    return torch.ops._C.cutlass_scaled_mm_supports_fp8(cuda_device_capability)
+
+
 def cutlass_scaled_mm(a: torch.Tensor, b: torch.Tensor, scale_a: torch.Tensor,
                       scale_b: torch.Tensor,
                       out_dtype: Type[torch.dtype]) -> torch.Tensor:

vllm/model_executor/layers/quantization/fp8.py

@@ -20,19 +20,8 @@
 def cutlass_fp8_supported() -> bool:
     capability = torch.cuda.get_device_capability()
     capability = capability[0] * 10 + capability[1]
-    major, minor = torch.version.cuda.split(".")
-    version = int(major) * 10 + int(minor)
-
-    # CUTLASS FP8 kernels need at least
-    #   CUDA 12.0 on SM90 systems (Hopper)
-    #   CUDA 12.4 on SM89 systems (Lovelace)
-    gpu_is_supported = False
-    if capability >= 90:
-        gpu_is_supported = version > 120
-    elif capability >= 89:
-        gpu_is_supported = version > 124
-
-    return gpu_is_supported
+
+    return ops.cutlass_scaled_mm_supports_fp8(capability)
 
 
 class Fp8Config(QuantizationConfig):