virtio-gpu: replace the surface with null surface when resetting

The primary guest scanout shows the booting screen right after reboot
but additional guest displays (i.e. max_ouptuts > 1) will keep displaying
the old frames until the guest virtio gpu driver gets initialized, which
could cause some confusion. A better way is to to replace the surface with
a place holder that tells the display is not active during the reset of
virtio-gpu device.

And to immediately update the surface with the place holder image after
the switch, displaychangelistener_gfx_switch needs to be called with
'update == TRUE' in dpy_gfx_replace_surface when the new surface is NULL.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
Acked-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-ID: <20230627224451.11739-1-dongwon.kim@intel.com>

hw/display/virtio-gpu.c

@@ -1397,6 +1397,7 @@ void virtio_gpu_reset(VirtIODevice *vdev)
     VirtIOGPU *g = VIRTIO_GPU(vdev);
     struct virtio_gpu_simple_resource *res, *tmp;
     struct virtio_gpu_ctrl_command *cmd;
+    int i = 0;
 
     QTAILQ_FOREACH_SAFE(res, &g->reslist, next, tmp) {
         virtio_gpu_resource_destroy(g, res);
@@ -1415,6 +1416,10 @@ void virtio_gpu_reset(VirtIODevice *vdev)
         g_free(cmd);
     }
 
+    for (i = 0; i < g->parent_obj.conf.max_outputs; i++) {
+        dpy_gfx_replace_surface(g->parent_obj.scanout[i].con, NULL);
+    }
+
     virtio_gpu_base_reset(VIRTIO_GPU_BASE(vdev));
 }
 

ui/console.c

@@ -1898,6 +1898,7 @@ void dpy_gfx_replace_surface(QemuConsole *con,
     static const char placeholder_msg[] = "Display output is not active.";
     DisplayState *s = con->ds;
     DisplaySurface *old_surface = con->surface;
+    DisplaySurface *new_surface = surface;
     DisplayChangeListener *dcl;
     int width;
     int height;
@@ -1911,19 +1912,19 @@ void dpy_gfx_replace_surface(QemuConsole *con,
             height = 480;
         }
 
-        surface = qemu_create_placeholder_surface(width, height, placeholder_msg);
+        new_surface = qemu_create_placeholder_surface(width, height, placeholder_msg);
     }
 
-    assert(old_surface != surface);
+    assert(old_surface != new_surface);
 
     con->scanout.kind = SCANOUT_SURFACE;
-    con->surface = surface;
-    dpy_gfx_create_texture(con, surface);
+    con->surface = new_surface;
+    dpy_gfx_create_texture(con, new_surface);
     QLIST_FOREACH(dcl, &s->listeners, next) {
         if (con != (dcl->con ? dcl->con : active_console)) {
             continue;
         }
-        displaychangelistener_gfx_switch(dcl, surface, FALSE);
+        displaychangelistener_gfx_switch(dcl, new_surface, surface ? FALSE : TRUE);
     }
     dpy_gfx_destroy_texture(con, old_surface);
     qemu_free_displaysurface(old_surface);