[ROCm][Bugfix][Model] Fix illegal memory access when running qwen3_moe models with rms_norm (Qwen3-235B-A22B, Qwen3-30B-A3B, etc.) (#26192)

Signed-off-by: Randall Smith <ransmith@amd.com>
Signed-off-by: Randall Smith <Randall.Smith@amd.com>
Signed-off-by: rasmith <Randall.Smith@amd.com>
Co-authored-by: Randall Smith <ransmith@amd.com>
Co-authored-by: Luka Govedič <ProExpertProg@users.noreply.github.com>

Author: 3 people

csrc/layernorm_kernels.cu

@@ -364,18 +364,26 @@ void rms_norm(torch::Tensor& out,     // [..., hidden_size]
   TORCH_CHECK(weight.is_contiguous());
 
   int hidden_size = input.size(-1);
-  int num_tokens = input.numel() / hidden_size;
-  int64_t input_stride = input.stride(-2);
+
+  // We cannot just use `input.stride(-2)` if the tensor is not row-major.
+  // Instead, we use a 2d view to get the second-innermost stride.
+  // That way the dimensions (except the last one) can be arbitrarily permuted.
+  torch::Tensor input_view = input.view({-1, hidden_size});
+
+  int num_tokens = input_view.numel() / hidden_size;
+  int64_t input_stride = input_view.stride(-2);
 
   dim3 grid(num_tokens);
   dim3 block(std::min(hidden_size, 1024));
-  const at::cuda::OptionalCUDAGuard device_guard(device_of(input));
+  const at::cuda::OptionalCUDAGuard device_guard(device_of(input_view));
   const cudaStream_t stream = at::cuda::getCurrentCUDAStream();
-  VLLM_DISPATCH_FLOATING_TYPES(input.scalar_type(), "rms_norm_kernel", [&] {
-    vllm::rms_norm_kernel<scalar_t><<<grid, block, 0, stream>>>(
-        out.data_ptr<scalar_t>(), input.data_ptr<scalar_t>(), input_stride,
-        weight.data_ptr<scalar_t>(), epsilon, num_tokens, hidden_size);
-  });
+  VLLM_DISPATCH_FLOATING_TYPES(
+      input_view.scalar_type(), "rms_norm_kernel", [&] {
+        vllm::rms_norm_kernel<scalar_t><<<grid, block, 0, stream>>>(
+            out.data_ptr<scalar_t>(), input_view.data_ptr<scalar_t>(),
+            input_stride, weight.data_ptr<scalar_t>(), epsilon, num_tokens,
+            hidden_size);
+      });
 }
 
 #define LAUNCH_FUSED_ADD_RMS_NORM(width)                                    \