rocm-systems/rocclr/runtime/device/rocm/rochostcall.hpp

//
// Copyright (c) 2019 Advanced Micro Devices, Inc. All rights reserved.
//

#pragma once

/** \file Support for invoking host services from the device.
 *
 *  A hostcall is a fixed-size request generated by a kernel running
 *  on the device, for some predefined service provided by the
 *  host. The life-cycle of a hostcall is as follows:
 *
 *  1. A workitem in the some kernel dispatch submits a request as a
 *     "packet" in a "hostcall buffer". The workitem blocks until it
 *     receives a response from the host.
 *
 *  2. A host thread called the "hostcall listener" notices the packet
 *     and invokes the desired service on the host.
 *
 *  3. When the service completes, the listener copies the response
 *     into the request packet. This unblocks the workitem, and the
 *     hostcall is said to be completed.
 *
 *  The hostcall listeners and buffers are managed by the VDI
 *  runtime. The typical flow is as follows:
 *
 *  - Create and launch one or more hostcall listeners.
 *
 *  - Create and initialize a distinct hostcall buffer for each
 *    command queue in hardware (e.g., an hsa_queue_t on ROCm).
 *
 *  - Register this buffer with the appropriate listener.
 *
 *  - When a buffer is no longer used, deregister and then free
 *    it. This usually happens when the corresponding hardware queue
 *    is freed.
 *
 *  - Destroy the listener(s) when they are no longer required. This must be
 *    done before exiting the application, so that the listener
 *    threads can join() correctly.
 *
 *  A single listener is sufficient to correctly handle all hostcall
 *  buffers created in the application. The client may also launch
 *  multiple listeners, as long the same hostcall buffer is not
 *  registered with multiple listeners.
 */

/** \brief Determine the buffer size to be allocated
 *  \param num_packets Number of packets to be supported.
 *  \return Required size, including any internal padding required for
 *          the packets and their headers.
 */
size_t getHostcallBufferSize(uint32_t num_packets);

/** \brief Return the required alignment for a hostcall buffer.
 */
uint32_t getHostcallBufferAlignment(void);

bool enableHostcalls(void* buffer, uint32_t numPackets, const void* queue);
void disableHostcalls(void* buffer, const void* queue);