[Stable-8.1.2 58/61] vfio/display: Fix missing update to set backing fields

[Michael Tokarev]

From: Alex Williamson <alex.williamson@redhat.com>

The below referenced commit renames scanout_width/height to
backing_width/height, but also promotes these fields in various portions
of the egl interface.  Meanwhile vfio dmabuf support has never used the
previous scanout fields and is therefore missed in the update.  This
results in a black screen when transitioning from ramfb to dmabuf display
when using Intel vGPU with these features.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1891
Link: https://lists.gnu.org/archive/html/qemu-devel/2023-08/msg02726.html
Fixes: 9ac06df8b684 ("virtio-gpu-udmabuf: correct naming of QemuDmaBuf size 
properties")
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Tested-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>
(cherry picked from commit 931150e56b056b120c868f94751722710df0b6a7)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

diff --git a/hw/vfio/display.c b/hw/vfio/display.c
index bec864f482..837d9e6a30 100644
--- a/hw/vfio/display.c
+++ b/hw/vfio/display.c
@@ -243,6 +243,8 @@ static VFIODMABuf *vfio_display_get_dmabuf(VFIOPCIDevice 
*vdev,
     dmabuf->dmabuf_id  = plane.dmabuf_id;
     dmabuf->buf.width  = plane.width;
     dmabuf->buf.height = plane.height;
+    dmabuf->buf.backing_width = plane.width;
+    dmabuf->buf.backing_height = plane.height;
     dmabuf->buf.stride = plane.stride;
     dmabuf->buf.fourcc = plane.drm_format;
     dmabuf->buf.modifier = plane.drm_format_mod;
-- 
2.39.2