virtio-gpu: clear command and fence queues on reset

It was never correct to not clear them.  Due to commit "3912e66a
virtio-vga: fix reset." this became more obvious though.  The virtio
rings get properly reset now, and trying to process the stale commands
will trigger an assert in the virtio core.
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20190314115358.26678-3-kraxel@redhat.com

hw/display/virtio-gpu.c

@@ -1356,6 +1356,7 @@ static 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;
 
     g->enable = 0;
@@ -1372,6 +1373,19 @@ static void virtio_gpu_reset(VirtIODevice *vdev)
         g->scanout[i].ds = NULL;
     }
 
+    while (!QTAILQ_EMPTY(&g->cmdq)) {
+        cmd = QTAILQ_FIRST(&g->cmdq);
+        QTAILQ_REMOVE(&g->cmdq, cmd, next);
+        g_free(cmd);
+    }
+
+    while (!QTAILQ_EMPTY(&g->fenceq)) {
+        cmd = QTAILQ_FIRST(&g->fenceq);
+        QTAILQ_REMOVE(&g->fenceq, cmd, next);
+        g->inflight--;
+        g_free(cmd);
+    }
+
 #ifdef CONFIG_VIRGL
     if (g->use_virgl_renderer) {
         if (g->renderer_blocked) {