Hi Oleksandr,
On 1/29/19 3:04 PM, Oleksandr Andrushchenko wrote:
From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
When GEM backing storage is allocated those are normal pages,
so there is no point using pgprot_writecombine while mmaping.
This fixes mismatch of buffer pages' memory attributes between
the frontend and backend which may cause screen artifacts.
Fixes: c575b7eeb89f ("drm/xen-front: Add support for Xen PV display frontend")
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
Suggested-by: Julien Grall <julien.grall@xxxxxxx>
---
drivers/gpu/drm/xen/xen_drm_front_gem.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/xen/xen_drm_front_gem.c b/drivers/gpu/drm/xen/xen_drm_front_gem.c
index d303a2e17f5e..9d5c03d7668d 100644
--- a/drivers/gpu/drm/xen/xen_drm_front_gem.c
+++ b/drivers/gpu/drm/xen/xen_drm_front_gem.c
@@ -235,8 +235,7 @@ static int gem_mmap_obj(struct xen_gem_object *xen_obj,
vma->vm_flags &= ~VM_PFNMAP;
vma->vm_flags |= VM_MIXEDMAP;
vma->vm_pgoff = 0;
- vma->vm_page_prot =
- pgprot_writecombine(vm_get_page_prot(vma->vm_flags));
+ vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
The patch looks good to me. It would be worth expanding the comment a
bit before to explain that we overwrite vm_page_prot to use cacheable
attribute as required by the Xen ABI.
With the comment updated:
Acked-by: Julien Grall <julien.grall@xxxxxxx>
Cheers,
--
Julien Grall
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