feat: Introduce StridedLayout, support wrapping external allocations in Buffer, add StridedMemoryView.from_buffer

cuda_core/cuda/core/experimental/_memory/_buffer.pxd

@@ -7,13 +7,22 @@ from libc.stdint cimport uintptr_t
 from cuda.core.experimental._stream cimport Stream
 
 
+cdef struct _MemAttrs:
+    int device_id
+    bint is_device_accessible
+    bint is_host_accessible
+
+
 cdef class Buffer:
     cdef:
         uintptr_t      _ptr
         size_t         _size
         MemoryResource _memory_resource
+        object         _owner
         object         _ptr_obj
         Stream         _alloc_stream
+        _MemAttrs      _mem_attrs
+        bint           _mem_attrs_inited
 
 
 cdef class MemoryResource:

cuda_core/cuda/core/experimental/_memory/_buffer.pyx

@@ -4,6 +4,7 @@
 
 from __future__ import annotations
 
+cimport cython
 from libc.stdint cimport uintptr_t
 
 from cuda.core.experimental._memory._device_memory_resource cimport DeviceMemoryResource
@@ -12,7 +13,9 @@ from cuda.core.experimental._memory cimport _ipc
 from cuda.core.experimental._stream cimport Stream_accept, Stream
 from cuda.core.experimental._utils.cuda_utils cimport (
     _check_driver_error as raise_if_driver_error,
+    HANDLE_RETURN,
 )
+from cuda.bindings cimport cydriver
 
 import abc
 from typing import TypeVar, Union
@@ -47,6 +50,8 @@ cdef class Buffer:
         self._memory_resource = None
         self._ptr_obj = None
         self._alloc_stream = None
+        self._owner = None
+        self._mem_attrs_inited = False
 
     def __init__(self, *args, **kwargs):
         raise RuntimeError("Buffer objects cannot be instantiated directly. "
@@ -55,14 +60,17 @@ cdef class Buffer:
     @classmethod
     def _init(
         cls, ptr: DevicePointerT, size_t size, mr: MemoryResource | None = None,
-        stream: Stream | None = None
+        stream: Stream | None = None, owner : object | None = None,
     ):
         cdef Buffer self = Buffer.__new__(cls)
         self._ptr = <uintptr_t>(int(ptr))
         self._ptr_obj = ptr
         self._size = size
+        if mr is not None and owner is not None:
+            raise ValueError("owner and memory resource cannot be both specified together")
         self._memory_resource = mr
         self._alloc_stream = <Stream>(stream) if stream is not None else None
+        self._owner = owner
         return self
 
     def __dealloc__(self):
@@ -74,7 +82,8 @@ cdef class Buffer:
 
     @staticmethod
     def from_handle(
-        ptr: DevicePointerT, size_t size, mr: MemoryResource | None = None
+        ptr: DevicePointerT, size_t size, mr: MemoryResource | None = None,
+        owner: object | None = None,
     ) -> Buffer:
         """Create a new :class:`Buffer` object from a pointer.
 
@@ -86,9 +95,13 @@ cdef class Buffer:
             Memory size of the buffer
         mr : :obj:`~_memory.MemoryResource`, optional
             Memory resource associated with the buffer
+        owner : object, optional
+            An object holding external allocation that the ``ptr`` points to.
+            The reference is kept as long as the buffer is alive.
+            The ``owner`` and ``mr`` cannot be specified together.
         """
         # TODO: It is better to take a stream for latter deallocation
-        return Buffer._init(ptr, size, mr=mr)
+        return Buffer._init(ptr, size, mr=mr, owner=owner)
 
     @classmethod
     def from_ipc_descriptor(
@@ -224,7 +237,9 @@ cdef class Buffer:
         """Return the device ordinal of this buffer."""
         if self._memory_resource is not None:
             return self._memory_resource.device_id
-        raise NotImplementedError("WIP: Currently this property only supports buffers with associated MemoryResource")
+        else:
+            Buffer_init_mem_attrs(self)
+            return self._mem_attrs.device_id
 
     @property
     def handle(self) -> DevicePointerT:
@@ -248,14 +263,18 @@ cdef class Buffer:
         """Return True if this buffer can be accessed by the GPU, otherwise False."""
         if self._memory_resource is not None:
             return self._memory_resource.is_device_accessible
-        raise NotImplementedError("WIP: Currently this property only supports buffers with associated MemoryResource")
+        else:
+            Buffer_init_mem_attrs(self)
+            return self._mem_attrs.is_device_accessible
 
     @property
     def is_host_accessible(self) -> bool:
         """Return True if this buffer can be accessed by the CPU, otherwise False."""
         if self._memory_resource is not None:
             return self._memory_resource.is_host_accessible
-        raise NotImplementedError("WIP: Currently this property only supports buffers with associated MemoryResource")
+        else:
+            Buffer_init_mem_attrs(self)
+            return self._mem_attrs.is_host_accessible
 
     @property
     def memory_resource(self) -> MemoryResource:
@@ -267,20 +286,93 @@ cdef class Buffer:
         """Return the memory size of this buffer."""
         return self._size
 
+    @property
+    def owner(self) -> object:
+        """Return the object holding external allocation."""
+        return self._owner
+
 
 # Buffer Implementation
 # ---------------------
 cdef inline void Buffer_close(Buffer self, stream):
     cdef Stream s
-    if self._ptr and self._memory_resource is not None:
-        s = Stream_accept(stream) if stream is not None else self._alloc_stream
-        self._memory_resource.deallocate(self._ptr, self._size, s)
+    if self._ptr:
+        if self._memory_resource is not None:
+            s = Stream_accept(stream) if stream is not None else self._alloc_stream
+            self._memory_resource.deallocate(self._ptr, self._size, s)
         self._ptr = 0
         self._memory_resource = None
+        self._owner = None
         self._ptr_obj = None
         self._alloc_stream = None
 
 
+cdef Buffer_init_mem_attrs(Buffer self):
+    if not self._mem_attrs_inited:
+        query_memory_attrs(self._mem_attrs, self._ptr)
+        self._mem_attrs_inited = True
+
+
+cdef int query_memory_attrs(_MemAttrs &out, uintptr_t ptr) except -1 nogil:
+    cdef unsigned int memory_type = 0
+    cdef int is_managed = 0
+    cdef int device_id = 0
+    _query_memory_attrs(memory_type, is_managed, device_id, <cydriver.CUdeviceptr>ptr)
+
+    if memory_type == 0:
+        # unregistered host pointer
+        out.is_host_accessible = True
+        out.is_device_accessible = False
+        out.device_id = -1
+    # for managed memory, the memory type can be CU_MEMORYTYPE_DEVICE,
+    # so we need to check it first not to falsely claim it is not
+    # host accessible.
+    elif (
+        is_managed
+        or memory_type == cydriver.CUmemorytype.CU_MEMORYTYPE_HOST
+    ):
+        # For pinned memory allocated with cudaMallocHost or paged-locked
+        # with cudaHostRegister, the memory_type is
+        # cydriver.CUmemorytype.CU_MEMORYTYPE_HOST.
+        # TODO(ktokarski): In some cases, the registered memory requires
+        # using different ptr for device and host, we could check
+        # cuMemHostGetDevicePointer and
+        # CU_DEVICE_ATTRIBUTE_CAN_USE_HOST_POINTER_FOR_REGISTERED_MEM
+        # to double check the device accessibility.
+        out.is_host_accessible = True
+        out.is_device_accessible = True
+        out.device_id = device_id
+    elif memory_type == cydriver.CUmemorytype.CU_MEMORYTYPE_DEVICE:
+        out.is_host_accessible = False
+        out.is_device_accessible = True
+        out.device_id = device_id
+    else:
+        raise ValueError(f"Unsupported memory type: {memory_type}")
+    return 0
+
+
+cdef inline int _query_memory_attrs(unsigned int& memory_type, int & is_managed, int& device_id, cydriver.CUdeviceptr ptr) except -1 nogil:
+    cdef cydriver.CUpointer_attribute attrs[3]
+    cdef uintptr_t vals[3]
+    attrs[0] = cydriver.CUpointer_attribute.CU_POINTER_ATTRIBUTE_MEMORY_TYPE
+    attrs[1] = cydriver.CUpointer_attribute.CU_POINTER_ATTRIBUTE_IS_MANAGED
+    attrs[2] = cydriver.CUpointer_attribute.CU_POINTER_ATTRIBUTE_DEVICE_ORDINAL
+    vals[0] = <uintptr_t><void*>&memory_type
+    vals[1] = <uintptr_t><void*>&is_managed
+    vals[2] = <uintptr_t><void*>&device_id
+
+    cdef cydriver.CUresult ret
+    ret = cydriver.cuPointerGetAttributes(3, attrs, <void**>vals, ptr)
+    if ret == cydriver.CUresult.CUDA_ERROR_NOT_INITIALIZED:
+        with cython.gil:
+            # Device class handles the cuInit call internally
+            from cuda.core.experimental import Device
+            Device()
+        ret = cydriver.cuPointerGetAttributes(3, attrs, <void**>vals, ptr)
+    HANDLE_RETURN(ret)
+    return 0
+
+
 cdef class MemoryResource:
     """Abstract base class for memory resources that manage allocation and
     deallocation of buffers.