virtio_gpu_virgl_init() may fail, leading to a further Qemu crash
because Qemu assumes it never fails. Check virtio_gpu_virgl_init()
return code and don't execute virtio commands on error. Failed
virtio_gpu_virgl_init() will result in a timed out virtio commands
for a guest OS.

Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 hw/display/virtio-gpu-gl.c     | 30 ++++++++++++++++++++++--------
 include/hw/virtio/virtio-gpu.h | 11 +++++++++--
 2 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/hw/display/virtio-gpu-gl.c b/hw/display/virtio-gpu-gl.c
index 29d20b01321c..ea3413aa566f 100644
--- a/hw/display/virtio-gpu-gl.c
+++ b/hw/display/virtio-gpu-gl.c
@@ -29,9 +29,14 @@ static void virtio_gpu_gl_update_cursor_data(VirtIOGPU *g,
                                              struct virtio_gpu_scanout *s,
                                              uint32_t resource_id)
 {
+    VirtIOGPUGL *gl = VIRTIO_GPU_GL(g);
     uint32_t width, height;
     uint32_t pixels, *data;
 
+    if (gl->renderer_state != RS_INITED) {
+        return;
+    }
+
     data = virgl_renderer_get_cursor_data(resource_id, &width, &height);
     if (!data) {
         return;
@@ -65,13 +70,22 @@ static void virtio_gpu_gl_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
         return;
     }
 
-    if (!gl->renderer_inited) {
-        virtio_gpu_virgl_init(g);
-        gl->renderer_inited = true;
-    }
-    if (gl->renderer_reset) {
-        gl->renderer_reset = false;
+    switch (gl->renderer_state) {
+    case RS_RESET:
         virtio_gpu_virgl_reset(g);
+        /* fallthrough */
+    case RS_START:
+        if (virtio_gpu_virgl_init(g)) {
+            gl->renderer_state = RS_INIT_FAILED;
+            return;
+        }
+
+        gl->renderer_state = RS_INITED;
+        break;
+    case RS_INIT_FAILED:
+        return;
+    case RS_INITED:
+        break;
     }
 
     cmd = virtqueue_pop(vq, sizeof(struct virtio_gpu_ctrl_command));
@@ -98,9 +112,9 @@ static void virtio_gpu_gl_reset(VirtIODevice *vdev)
      * GL functions must be called with the associated GL context in main
      * thread, and when the renderer is unblocked.
      */
-    if (gl->renderer_inited && !gl->renderer_reset) {
+    if (gl->renderer_state == RS_INITED) {
         virtio_gpu_virgl_reset_scanout(g);
-        gl->renderer_reset = true;
+        gl->renderer_state = RS_RESET;
     }
 }
 
diff --git a/include/hw/virtio/virtio-gpu.h b/include/hw/virtio/virtio-gpu.h
index 18b6c3b3a226..71775243e99b 100644
--- a/include/hw/virtio/virtio-gpu.h
+++ b/include/hw/virtio/virtio-gpu.h
@@ -222,11 +222,18 @@ struct VirtIOGPUClass {
                              Error **errp);
 };
 
+/* VirtIOGPUGL renderer states */
+typedef enum {
+    RS_START,       /* starting state */
+    RS_INIT_FAILED, /* failed initialisation */
+    RS_INITED,      /* initialised and working */
+    RS_RESET,       /* inited and reset pending, moves to start after reset */
+} RenderState;
+
 struct VirtIOGPUGL {
     struct VirtIOGPU parent_obj;
 
-    bool renderer_inited;
-    bool renderer_reset;
+    RenderState renderer_state;
 
     QEMUTimer *fence_poll;
     QEMUTimer *print_stats;
-- 
2.47.0