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Commit 24ded292 authored by Oleksandr Andrushchenko's avatar Oleksandr Andrushchenko
Browse files

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: c575b7ee ("drm/xen-front: Add support for Xen PV display frontend")

Signed-off-by: default avatarOleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Suggested-by: default avatarJulien Grall <julien.grall@arm.com>
Acked-by: default avatarJulien Grall <julien.grall@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190129150422.19867-1-andr2000@gmail.com
parent 938010ab

drivers/gpu/drm/xen/xen_drm_front_gem.c

+10 −3
Original line number Diff line number Diff line
@@ -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,