clEnqueueReadBuffer fails on IGPUs for mapped host-buffer desinations #866
Description
Consider the following snippet which I believe to be a valid use of the OpenCL API:
#include <CL/cl.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #define CHECK(err, msg) \ if (err != CL_SUCCESS) { \ fprintf(stderr, "%s failed (%d)\n", msg, err); \ exit(1); \ } int main(void) { cl_int err; cl_platform_id platform; CHECK(clGetPlatformIDs(1, &platform, NULL), "clGetPlatformIDs"); cl_device_id device; CHECK(clGetDeviceIDs(platform, CL_DEVICE_TYPE_DEFAULT, 1, &device, NULL), "clGetDeviceIDs"); cl_context context = clCreateContext(NULL, 1, &device, NULL, NULL, &err); CHECK(err, "clCreateContext"); cl_command_queue queue = clCreateCommandQueueWithProperties(context, device, 0, &err); CHECK(err, "clCreateCommandQueue"); const size_t N = 16; const size_t bytes = N * sizeof(float); cl_mem dev_buf = clCreateBuffer(context, CL_MEM_READ_WRITE, bytes, NULL, &err); CHECK(err, "clCreateBuffer dev_buf"); float pattern = 42.0f; // fill value CHECK(clEnqueueFillBuffer(queue, dev_buf, &pattern, sizeof(float), 0, bytes, 0, NULL, NULL), "clEnqueueFillBuffer"); cl_mem host_buf = clCreateBuffer(context, CL_MEM_READ_WRITE | CL_MEM_ALLOC_HOST_PTR, bytes, NULL, &err); CHECK(err, "clCreateBuffer host_buf"); void *host_ptr = clEnqueueMapBuffer(queue, host_buf, CL_TRUE, CL_MAP_WRITE, 0, bytes, 0, NULL, NULL, &err); CHECK(err, "clEnqueueMapBuffer"); err = clEnqueueReadBuffer(queue, dev_buf, CL_FALSE, 0, bytes, host_ptr, 0, NULL, NULL); CHECK(err, "clEnqueueReadBuffer (non-blocking)"); CHECK(clFinish(queue), "clFinish"); CHECK(clEnqueueUnmapMemObject(queue, host_buf, host_ptr, 0, NULL, NULL), "clEnqueueUnmapMemObject"); clFinish(queue); clReleaseMemObject(dev_buf); clReleaseMemObject(host_buf); clReleaseCommandQueue(queue); clReleaseContext(context); return 0; }Running this on an NVIDIA GPU or an Intel A770m works as expected. However, on my IGPU (TigerLake-H GT1) it fails with:
clEnqueueReadBuffer (non-blocking) failed (-5)
Changing to an ordinary buffer (from malloc) appears to work, as does changing to blocking reads. My runtime version is 25.40.35563.4 and I am on a 6.17.5 kernel with the i915 module.