From: Robin Murphy <robin.murphy@xxxxxxx> 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@xxxxxxxx> Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx> Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@xxxxxxxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20211013143654.39031-1-alyssa@xxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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); Patches currently in stable-queue which might be from robin.murphy@xxxxxxx are queue-5.15/drm-cma-helper-set-vm_dontexpand-for-mmap.patch