C Specification

To enqueue a command that will allow the host to update a region of a SVM buffer, call the function

cl_int clEnqueueSVMMap(
    cl_command_queue command_queue,
    cl_bool blocking_map,
    cl_map_flags flags,
    void* svm_ptr,
    size_t size,
    cl_uint num_events_in_wait_list,
    const cl_event* event_wait_list,
    cl_event* event);

Parameters

  • command_queue must be a valid host command-queue.

  • blocking_map indicates if the map operation is blocking or non-blocking.

  • map_flags is a bit-field and is described in the Memory Map Flags table.

  • svm_ptr and size are a pointer to a memory region and size in bytes that will be updated by the host. If svm_ptr is allocated using clSVMAlloc then it must be allocated from the same context from which command_queue was created. Otherwise the behavior is undefined.

  • event_wait_list and num_events_in_wait_list specify events that need to complete before this particular command can be executed. If event_wait_list is NULL, then this particular command does not wait on any event to complete. If event_wait_list is NULL, num_events_in_wait_list must be 0. If event_wait_list is not NULL, the list of events pointed to by event_wait_list must be valid and num_events_in_wait_list must be greater than 0. The events specified in event_wait_list act as synchronization points. The context associated with events in event_wait_list and command_queue must be the same. The memory associated with event_wait_list can be reused or freed after the function returns.

  • event returns an event object that identifies this particular command and can be used to query or queue a wait for this particular command to complete. event can be NULL in which case it will not be possible for the application to query the status of this command or queue a wait for this command to complete. clEnqueueBarrierWithWaitList can be used instead. If the event_wait_list and the event arguments are not NULL, the event argument should not refer to an element of the event_wait_list array.

Description

If blocking_map is CL_​TRUE, clEnqueueSVMMap does not return until the application can access the contents of the SVM region specified by svm_ptr and size on the host.

If blocking_map is CL_​FALSE i.e. map operation is non-blocking, the region specified by svm_ptr and size cannot be used until the map command has completed. The event argument returns an event object which can be used to query the execution status of the map command. When the map command is completed, the application can access the contents of the region specified by svm_ptr and size.

Note that since we are enqueuing a command with a SVM buffer, the region is already mapped in the host address space.

clEnqueueSVMMap returns CL_​SUCCESS if the function is executed successfully. Otherwise, it returns one of the following errors:

  • CL_​INVALID_​COMMAND_​QUEUE if command_queue is not a valid host command-queue.

  • CL_​INVALID_​CONTEXT if context associated with command_queue and events in event_wait_list are not the same.

  • CL_​INVALID_​VALUE if svm_ptr is NULL.

  • CL_​INVALID_​VALUE if size is 0 or if values specified in map_flags are not valid.

  • CL_​INVALID_​EVENT_​WAIT_​LIST if event_wait_list is NULL and num_events_in_wait_list > 0, or event_wait_list is not NULL and num_events_in_wait_list is 0, or if event objects in event_wait_list are not valid events.

  • CL_​EXEC_​STATUS_​ERROR_​FOR_​EVENTS_​IN_​WAIT_​LIST if the map operation is blocking and the execution status of any of the events in event_wait_list is a negative integer value.

  • CL_​OUT_​OF_​RESOURCES if there is a failure to allocate resources required by the OpenCL implementation on the device.

  • CL_​OUT_​OF_​HOST_​MEMORY if there is a failure to allocate resources required by the OpenCL implementation on the host.

See Also

Document Notes

For more information, see the OpenCL Specification

This page is extracted from the OpenCL Specification. Fixes and changes should be made to the Specification, not directly.

Copyright (c) 2014-2020 Khronos Group. This work is licensed under a Creative Commons Attribution 4.0 International License.