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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: c575b7eeb8 ("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
hifive-unleashed-5.1
Oleksandr Andrushchenko 2019-01-29 17:04:22 +02:00
parent 938010ab07
commit 24ded292a5
1 changed files with 10 additions and 3 deletions
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13
drivers/gpu/drm/xen/xen_drm_front_gem.c
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@ -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,