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From:   Gerd Hoffmann <kraxel@redhat.com>
To:     dri-devel@lists.freedesktop.org
Cc:     gurchetansingh@chromium.org, Gerd Hoffmann <kraxel@redhat.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        virtualization@lists.linux-foundation.org (open list:VIRTIO GPU DRIVER),
        linux-kernel@vger.kernel.org (open list)
Subject: [PATCH] drm/virtio: fix mmap page attributes
Date:   Tue, 10 Dec 2019 09:57:59 +0100
Message-Id: <20191210085759.14763-1-kraxel@redhat.com>
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

virtio-gpu uses cached mappings.  shmem helpers use writecombine though.
So roll our own mmap function, wrapping drm_gem_shmem_mmap(), to tweak
vm_page_prot accordingly.

Reported-by: Gurchetan Singh <gurchetansingh@chromium.org>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 drivers/gpu/drm/virtio/virtgpu_object.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virt=
io/virtgpu_object.c
index 017a9e0fc3bb..158610902054 100644
--- a/drivers/gpu/drm/virtio/virtgpu_object.c
+++ b/drivers/gpu/drm/virtio/virtgpu_object.c
@@ -75,6 +75,22 @@ static void virtio_gpu_free_object(struct drm_gem_object=
 *obj)
 =09drm_gem_shmem_free_object(obj);
 }
=20
+static int virtio_gpu_gem_mmap(struct drm_gem_object *obj, struct vm_area_=
struct *vma)
+{
+=09pgprot_t prot;
+=09int ret;
+
+=09ret =3D drm_gem_shmem_mmap(obj, vma);
+=09if (ret < 0)
+=09=09return ret;
+
+=09/* virtio-gpu needs normal caching, so clear writecombine */
+=09prot =3D vm_get_page_prot(vma->vm_flags);
+=09prot =3D pgprot_decrypted(prot);
+=09vma->vm_page_prot =3D prot;
+=09return 0;
+}
+
 static const struct drm_gem_object_funcs virtio_gpu_gem_funcs =3D {
 =09.free =3D virtio_gpu_free_object,
 =09.open =3D virtio_gpu_gem_object_open,
@@ -86,7 +102,7 @@ static const struct drm_gem_object_funcs virtio_gpu_gem_=
funcs =3D {
 =09.get_sg_table =3D drm_gem_shmem_get_sg_table,
 =09.vmap =3D drm_gem_shmem_vmap,
 =09.vunmap =3D drm_gem_shmem_vunmap,
-=09.mmap =3D &drm_gem_shmem_mmap,
+=09.mmap =3D &virtio_gpu_gem_mmap,
 };
=20
 struct drm_gem_object *virtio_gpu_create_object(struct drm_device *dev,
--=20
2.18.1