[BugFix] Fix import error on non-blackwell machines (vllm-project#21020)

Signed-off-by: Lucas Wilkinson <lwilkins@redhat.com>

Author: LucasWilkinson

csrc/attention/mla/sm100_cutlass_mla_kernel.cu

@@ -18,6 +18,7 @@ limitations under the License.
  * Taken from SGLANG PR https://github.com/sgl-project/sglang/pull/6929
  * by Alcanderian JieXin Liang
  */
+#include "core/registration.h"
 
 #include <ATen/cuda/CUDAContext.h>
 #include <c10/cuda/CUDAGuard.h>
@@ -270,4 +271,13 @@ int64_t sm100_cutlass_mla_get_workspace_size(int64_t max_seq_len, int64_t num_ba
 }
 
 #endif
+
+TORCH_LIBRARY_IMPL_EXPAND(TORCH_EXTENSION_NAME, CUDA, m) {
+  m.impl("sm100_cutlass_mla_decode", &sm100_cutlass_mla_decode);
+}
+
+TORCH_LIBRARY_IMPL_EXPAND(TORCH_EXTENSION_NAME, CatchAll, m) {
+  m.impl("sm100_cutlass_mla_get_workspace_size", &sm100_cutlass_mla_get_workspace_size);
+}
+
 // clang-format on

csrc/ops.h

@@ -167,19 +167,6 @@ void cutlass_mla_decode(torch::Tensor const& out, torch::Tensor const& q_nope,
                         torch::Tensor const& seq_lens,
                         torch::Tensor const& page_table, double scale);
 
-void sm100_cutlass_mla_decode(
-    torch::Tensor const& out, torch::Tensor const& q_nope,
-    torch::Tensor const& q_pe, torch::Tensor const& kv_c_and_k_pe_cache,
-    torch::Tensor const& seq_lens, torch::Tensor const& page_table,
-    torch::Tensor const& workspace, double sm_scale,
-    int64_t num_kv_splits =
-        1 /* Set to 1 to avoid cuda_graph issue by default. */);
-
-int64_t sm100_cutlass_mla_get_workspace_size(
-    int64_t max_seq_len, int64_t num_batches, int64_t sm_count = 0,
-    int64_t num_kv_splits =
-        1 /* Set to 1 to avoid cuda_graph issue by default. */);
-
 torch::Tensor get_cuda_view_from_cpu_tensor(torch::Tensor& cpu_tensor);
 
 #ifndef USE_ROCM

csrc/torch_bindings.cpp

@@ -521,15 +521,14 @@ TORCH_LIBRARY_EXPAND(TORCH_EXTENSION_NAME, ops) {
       "                         Tensor page_table, Tensor workspace, float "
       "scale,"
       "                         int num_kv_splits) -> ()");
-  ops.impl("sm100_cutlass_mla_decode", torch::kCUDA, &sm100_cutlass_mla_decode);
+  // conditionally compiled so impl in source file
 
   // SM100 CUTLASS MLA workspace
   ops.def(
       "sm100_cutlass_mla_get_workspace_size(int max_seq_len, int num_batches,"
       "                                     int sm_count, int num_kv_splits) "
       "-> int");
-  ops.impl("sm100_cutlass_mla_get_workspace_size",
-           &sm100_cutlass_mla_get_workspace_size);
+  // conditionally compiled so impl in source file
 
   // Compute NVFP4 block quantized tensor.
   ops.def(