Hi, On Thu, Nov 30, 2023 at 06:14:16PM +0100, Marco Pagani wrote: > This patch introduces an initial KUnit test suite for GEM objects > backed by shmem buffers. > > Suggested-by: Javier Martinez Canillas <javierm@xxxxxxxxxx> > Signed-off-by: Marco Pagani <marpagan@xxxxxxxxxx> When running this in qemu, I get lots of warnings backtraces in the drm core. WARNING: CPU: 0 PID: 1341 at drivers/gpu/drm/drm_gem_shmem_helper.c:327 WARNING: CPU: 0 PID: 1341 at drivers/gpu/drm/drm_gem_shmem_helper.c:173 WARNING: CPU: 0 PID: 1341 at drivers/gpu/drm/drm_gem_shmem_helper.c:385 WARNING: CPU: 0 PID: 1341 at drivers/gpu/drm/drm_gem_shmem_helper.c:211 WARNING: CPU: 0 PID: 1345 at kernel/dma/mapping.c:194 WARNING: CPU: 0 PID: 1347 at drivers/gpu/drm/drm_gem_shmem_helper.c:429 WARNING: CPU: 0 PID: 1349 at drivers/gpu/drm/drm_gem_shmem_helper.c:445 It looks like dma_resv_assert_held() asserts each time it is executed. The backtrace in kernel/dma/mapping.c is triggered by if (WARN_ON_ONCE(!dev->dma_mask)) return 0; in __dma_map_sg_attrs(). Is this a possible problem in the test code, or can it be caused by some limitations or bugs in the qemu emulation ? If so, do you have any thoughts or ideas what those limitations / bugs might be ? Thanks, Guenter
