The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 59f39bfa6553d598cb22f694d45e89547f420d85 Mon Sep 17 00:00:00 2001 From: Robin Murphy robin.murphy@arm.com Date: Wed, 13 Oct 2021 10:36:54 -0400 Subject: [PATCH] drm/cma-helper: Set VM_DONTEXPAND for mmap

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@...

diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c b/drivers/gpu/drm/drm_gem_cma_helper.c index cefd0cbf9deb..dc275c466c9c 100644 --- a/drivers/gpu/drm/drm_gem_cma_helper.c +++ b/drivers/gpu/drm/drm_gem_cma_helper.c @@ -512,6 +512,7 @@ int drm_gem_cma_mmap(struct drm_gem_cma_object *cma_obj, struct vm_area_struct * */ vma->vm_pgoff -= drm_vma_node_start(&obj->vma_node); vma->vm_flags &= ~VM_PFNMAP; + vma->vm_flags |= VM_DONTEXPAND;

if (cma_obj->map_noncoherent) { vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);