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authorOleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>2019-01-29 17:04:22 +0200
committerOleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>2019-02-04 08:39:31 +0200
commit24ded292a5c2ed476f01c77fee65f8320552cd27 (patch)
tree81516989c8309026fc77638c4bbb7699540f003b
parent938010ab072221f9b396770bbe78001ee3b74302 (diff)
drm/xen-front: Fix mmap attributes for display buffers
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@epam.com> Suggested-by: Julien Grall <julien.grall@arm.com> Acked-by: Julien Grall <julien.grall@arm.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190129150422.19867-1-andr2000@gmail.com
-rw-r--r--drivers/gpu/drm/xen/xen_drm_front_gem.c13
1 files changed, 10 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..53c376d55fcf 100644
--- a/drivers/gpu/drm/xen/xen_drm_front_gem.c
+++ b/drivers/gpu/drm/xen/xen_drm_front_gem.c
@@ -235,8 +235,14 @@ 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));
+ /*
+ * According to Xen on ARM ABI (xen/include/public/arch-arm.h):
+ * all memory which is shared with other entities in the system
+ * (including the hypervisor and other guests) must reside in memory
+ * which is mapped as Normal Inner Write-Back Outer Write-Back
+ * Inner-Shareable.
+ */
+ vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
/*
* vm_operations_struct.fault handler will be called if CPU access
@@ -282,8 +288,9 @@ void *xen_drm_front_gem_prime_vmap(struct drm_gem_object *gem_obj)
if (!xen_obj->pages)
return NULL;
+ /* Please see comment in gem_mmap_obj on mapping and attributes. */
return vmap(xen_obj->pages, xen_obj->num_pages,
- VM_MAP, pgprot_writecombine(PAGE_KERNEL));
+ VM_MAP, PAGE_KERNEL);
}
void xen_drm_front_gem_prime_vunmap(struct drm_gem_object *gem_obj,