ui: introduce vfio_display_reset

ui: introduce vfio_display_reset

During guest OS reboot, guest framebuffer is invalid. It will cause
bugs, if the invalid guest framebuffer is still used by host.

This patch is to introduce vfio_display_reset which is invoked
during vfio display reset. This vfio_display_reset function is used
to release the invalid display resource, disable scanout mode and
replace the invalid surface with QemuConsole's DisplaySurafce.

This patch can fix the GPU hang issue caused by gd_egl_draw during
guest OS reboot.

Changes v3->v4:
 - Move dma-buf based display check into the vfio_display_reset().
   (Gerd)

Changes v2->v3:
 - Limit vfio_display_reset to dma-buf based vfio display. (Gerd)

Changes v1->v2:
 - Use dpy_gfx_update_full() update screen after reset. (Gerd)
 - Remove dpy_gfx_switch_surface(). (Gerd)

Signed-off-by: Tina Zhang <tina.zhang@intel.com>
Message-id: 1524820266-27079-3-git-send-email-tina.zhang@intel.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>