From: Robin Murphy robin.murphy@arm.com
commit 59f39bfa6553d598cb22f694d45e89547f420d85 upstream.
drm_gem_cma_mmap() cannot assume every implementation of dma_mmap_wc() will end up calling remap_pfn_range() (which happens to set the relevant vma flag, among others), so in order to make sure expectations around VM_DONTEXPAND are met, let it explicitly set the flag like most other GEM mmap implementations do.
This avoids repeated warnings on a small minority of systems where the display is behind an IOMMU, and has a simple driver which does not override drm_gem_cma_default_funcs. Arm hdlcd is an in-tree affected driver. Out-of-tree, the Apple DCP driver is affected; this fix is required for DCP to be mainlined.
[Alyssa: Update commit message.]
Fixes: c40069cb7bd6 ("drm: add mmap() to drm_gem_object_funcs") Acked-by: Daniel Vetter daniel@ffwll.ch Signed-off-by: Robin Murphy robin.murphy@arm.com Signed-off-by: Alyssa Rosenzweig alyssa.rosenzweig@collabora.com Link: https://patchwork.freedesktop.org/patch/msgid/20211013143654.39031-1-alyssa@... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/drm_gem_cma_helper.c | 1 + 1 file changed, 1 insertion(+)
--- a/drivers/gpu/drm/drm_gem_cma_helper.c +++ b/drivers/gpu/drm/drm_gem_cma_helper.c @@ -515,6 +515,7 @@ int drm_gem_cma_mmap(struct drm_gem_obje */ vma->vm_pgoff -= drm_vma_node_start(&obj->vma_node); vma->vm_flags &= ~VM_PFNMAP; + vma->vm_flags |= VM_DONTEXPAND;
cma_obj = to_drm_gem_cma_obj(obj);