On Wed, Oct 13, 2021 at 10:36:54AM -0400, Alyssa Rosenzweig wrote: > From: Robin Murphy <robin.murphy@xxxxxxx> > > 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. How/where does this warn? Also there should be a lot more drivers than just these two which have an iommu for the display block, so this not working is definitely a more wide-spread issue. -Daniel > Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx> > Reviewed-and-tested-by: Alyssa Rosenzweig <alyssa@xxxxxxxxxxxxx> > --- > drivers/gpu/drm/drm_gem_cma_helper.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c > index d53388199f34..63e48d98263d 100644 > --- a/drivers/gpu/drm/drm_gem_cma_helper.c > +++ b/drivers/gpu/drm/drm_gem_cma_helper.c > @@ -510,6 +510,7 @@ int drm_gem_cma_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma) > */ > 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); > > -- > 2.30.2 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
