Optional extension for green context (#9231)

sgl-kernel/CMakeLists.txt

@@ -274,7 +274,6 @@ set(SOURCES
     "csrc/kvcacheio/transfer.cu"
     "csrc/speculative/eagle_utils.cu"
     "csrc/speculative/packbit.cu"
-    "csrc/spatial/greenctx_stream.cu"
     "csrc/speculative/speculative_sampling.cu"
     "csrc/memory/store.cu"
     "${repo-flashinfer_SOURCE_DIR}/csrc/norm.cu"
@@ -417,6 +416,18 @@ if (SGL_KERNEL_ENABLE_FA3)
     target_compile_definitions(flash_ops PRIVATE ${FLASH_OPS_COMPILE_DEFS})
 endif()
 
+# Build spatial_ops as a separate, optional extension for green contexts
+set(SPATIAL_SOURCES
+    "csrc/spatial/greenctx_stream.cu"
+    "csrc/spatial_extension.cc"
+)
+
+Python_add_library(spatial_ops MODULE USE_SABI ${SKBUILD_SABI_VERSION} WITH_SOABI ${SPATIAL_SOURCES})
+target_compile_options(spatial_ops PRIVATE $<$<COMPILE_LANGUAGE:CUDA>:${SGL_KERNEL_CUDA_FLAGS}>)
+target_link_libraries(spatial_ops PRIVATE ${TORCH_LIBRARIES} c10 cuda)
+install(TARGETS spatial_ops LIBRARY DESTINATION sgl_kernel)
+
+
 # ============================ DeepGEMM (JIT) ============================= #
 # Create a separate library for DeepGEMM's Python API.
 # This keeps its compilation isolated from the main common_ops.

sgl-kernel/csrc/common_extension.cc

@@ -433,12 +433,6 @@ TORCH_LIBRARY_FRAGMENT(sgl_kernel, m) {
       "qserve_w4a8_per_group_gemm(Tensor _in_feats, Tensor _kernel, Tensor _zeros, Tensor _scales_i8, Tensor _wscales, "
       "Tensor _ascales, Tensor! _out_feats) -> ()");
   m.impl("qserve_w4a8_per_group_gemm", torch::kCUDA, &qserve_w4a8_per_group_gemm);
-
-  /*
-   * From csrc/spatial
-   */
-  m.def("create_greenctx_stream_by_value(int smA, int smB, int device) -> int[]");
-  m.impl("create_greenctx_stream_by_value", &create_greenctx_stream_by_value);
 }
 
 REGISTER_EXTENSION(common_ops)

sgl-kernel/csrc/spatial/greenctx_stream.cu

@@ -42,6 +42,7 @@ static std::vector<int64_t> create_greenctx_stream_direct_dynamic(CUgreenCtx gct
   // This symbol is introduced in CUDA 12.5
   const static auto pfn = probe_cuGreenCtxStreamCreate();
   if (!pfn) {
+    TORCH_WARN("cuGreenCtxStreamCreate(cuda>=12.5) is not available, using fallback");
     return create_greenctx_stream_fallback(gctx);
   }
 
@@ -55,17 +56,12 @@ static std::vector<int64_t> create_greenctx_stream_direct_dynamic(CUgreenCtx gct
 std::vector<int64_t> create_greenctx_stream_by_value(int64_t smA, int64_t smB, int64_t device) {
   CUDA_DRV(cuDriverGetVersion(&CUDA_DRIVER_VERSION));
 
-  if (CUDA_DRIVER_VERSION < 12040) {
-    TORCH_CHECK(false, "Green Contexts feature requires CUDA Toolkit 12.4 or newer.");
-  }
-
   CUgreenCtx gctx[3];
   CUdevResourceDesc desc[3];
   CUdevResource input;
   CUdevResource resources[4];
-  if (smA <= 0 || smB <= 0) {
-    TORCH_CHECK(false, "SM counts must be positive");
-  }
+
+  TORCH_CHECK(smA > 0 && smB > 0, "SM counts must be positive");
 
   CUDA_DRV(cuDeviceGetDevResource((CUdevice)device, &input, CU_DEV_RESOURCE_TYPE_SM));
 

sgl-kernel/csrc/spatial_extension.cc

@@ -0,0 +1,29 @@
+/* Copyright 2025 SGLang Team. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#include <torch/all.h>
+#include <torch/library.h>
+
+#include "sgl_kernel_ops.h"
+
+TORCH_LIBRARY_FRAGMENT(sgl_kernel, m) {
+  /*
+   * From csrc/spatial
+   */
+  m.def("create_greenctx_stream_by_value(int smA, int smB, int device) -> int[]");
+  m.impl("create_greenctx_stream_by_value", &create_greenctx_stream_by_value);
+}
+
+REGISTER_EXTENSION(spatial_ops)

sgl-kernel/python/sgl_kernel/__init__.py

@@ -92,7 +92,20 @@ from sgl_kernel.sampling import (
     top_p_renorm_prob,
     top_p_sampling_from_probs,
 )
-from sgl_kernel.spatial import create_greenctx_stream_by_value, get_sm_available
+
+
+def create_greenctx_stream_by_value(*args, **kwargs):
+    from sgl_kernel.spatial import create_greenctx_stream_by_value as _impl
+
+    return _impl(*args, **kwargs)
+
+
+def get_sm_available(*args, **kwargs):
+    from sgl_kernel.spatial import get_sm_available as _impl
+
+    return _impl(*args, **kwargs)
+
+
 from sgl_kernel.speculative import (
     build_tree_kernel_efficient,
     segment_packbits,

sgl-kernel/python/sgl_kernel/spatial.py

@@ -1,6 +1,17 @@
 import torch
 from torch.cuda.streams import ExternalStream
 
+try:
+    from . import spatial_ops  # triggers TORCH extension registration
+except Exception as _e:
+    _spatial_import_error = _e
+else:
+    _spatial_import_error = None
+
+_IMPORT_ERROR = ImportError(
+    "Failed to load sgl_kernel.spatial_ops extension. Ensure CUDA Driver >= 12.4"
+)
+
 
 def create_greenctx_stream_by_value(
     SM_a: int, SM_b: int, device_id: int = None
@@ -14,11 +25,8 @@ def create_greenctx_stream_by_value(
     Returns:
         tuple[ExternalStream, ExternalStream]: The two streams.
     """
-    if torch.version.cuda < "12.4":
-        raise RuntimeError(
-            "Green Contexts feature requires CUDA Toolkit 12.4 or newer."
-        )
-
+    if _spatial_import_error is not None:
+        raise _IMPORT_ERROR from _spatial_import_error
     if device_id is None:
         device_id = torch.cuda.current_device()
 
@@ -42,6 +50,8 @@ def get_sm_available(device_id: int = None) -> int:
     Returns:
         int: The SMs available.
     """
+    if _spatial_import_error is not None:
+        raise _IMPORT_ERROR from _spatial_import_error
     if device_id is None:
         device_id = torch.cuda.current_device()