Xfail MCDM mempool OOM with older bindings

Keep cuda-core tests using published older cuda-bindings wheels from failing when the shared mempool xfail helper is unavailable.

Author: rwgk

cuda_bindings/cuda/bindings/_test_helpers/mempool.py

@@ -8,6 +8,9 @@
 from cuda.bindings import driver, runtime
 
 
+# Keep in sync with the fallback in cuda_core/tests/conftest.py. The cuda_core
+# copy is intentionally simpler because it only handles cuda_core CUDAError
+# exceptions when this helper is absent from older published bindings.
 def is_windows_mcdm_device(device=0):
     if sys.platform != "win32":
         return False

cuda_core/tests/conftest.py

@@ -34,10 +34,50 @@
     from cuda.bindings._test_helpers.mempool import xfail_if_mempool_oom
 except ModuleNotFoundError:
     # Older cuda.bindings artifacts (for example 12.9.x backports) do not ship
-    # this helper yet. In that case, keep the primary failure visible instead of
-    # xfail-ing the known Windows MCDM mempool setup issue.
+    # this helper yet. Keep the fallback local so tests against published
+    # bindings still xfail the known Windows MCDM mempool setup issue.
+    #
+    # Keep in sync with cuda_bindings/cuda/bindings/_test_helpers/mempool.py.
+    # This copy is intentionally simpler because it only handles cuda_core
+    # CUDAError exceptions when the shared helper is absent.
+    def _is_windows_mcdm_device(device=0):
+        if sys.platform != "win32":
+            return False
+        import cuda.bindings.nvml as nvml
+
+        device_id = int(getattr(device, "device_id", device))
+        (err,) = driver.cuInit(0)
+        if err != driver.CUresult.CUDA_SUCCESS:
+            return False
+        err, pci_bus_id = driver.cuDeviceGetPCIBusId(13, device_id)
+        if err != driver.CUresult.CUDA_SUCCESS:
+            return False
+        pci_bus_id = pci_bus_id.split(b"\x00", 1)[0].decode("ascii")
+        nvml.init_v2()
+        try:
+            handle = nvml.device_get_handle_by_pci_bus_id_v2(pci_bus_id)
+            current, _ = nvml.device_get_driver_model_v2(handle)
+            return current == nvml.DriverModel.DRIVER_MCDM
+        finally:
+            nvml.shutdown()
+
     def xfail_if_mempool_oom(err_or_exc, api_name=None, device=0):
-        return
+        if api_name is not None and not isinstance(api_name, str):
+            device = api_name
+            api_name = None
+
+        if "CUDA_ERROR_OUT_OF_MEMORY" not in str(err_or_exc):
+            return
+        try:
+            is_windows_mcdm = _is_windows_mcdm_device(device)
+        except Exception:
+            # If MCDM detection fails, leave the primary test failure visible.
+            return
+        if not is_windows_mcdm:
+            return
+
+        api_context = f"{api_name} " if api_name else ""
+        pytest.xfail(f"{api_context}could not reserve VA for mempool operations on Windows MCDM")
 
 
 # Import shared test helpers for tests across subprojects.