virtio-gpu: add support to enable/disable command processing

So we can stop rendering for a while in case we have to.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

hw/display/virtio-gpu-3d.c

@@ -554,7 +554,8 @@ static void virtio_gpu_fence_poll(void *opaque)
     VirtIOGPU *g = opaque;
 
     virgl_renderer_poll();
-    if (g->inflight) {
+    virtio_gpu_process_cmdq(g);
+    if (!QTAILQ_EMPTY(&g->cmdq) || !QTAILQ_EMPTY(&g->fenceq)) {
         timer_mod(g->fence_poll, qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) + 10);
     }
 }

hw/display/virtio-gpu.c

@@ -755,7 +755,7 @@ static void virtio_gpu_handle_cursor_cb(VirtIODevice *vdev, VirtQueue *vq)
     qemu_bh_schedule(g->cursor_bh);
 }
 
-static void virtio_gpu_process_cmdq(VirtIOGPU *g)
+void virtio_gpu_process_cmdq(VirtIOGPU *g)
 {
     struct virtio_gpu_ctrl_command *cmd;
 
@@ -765,6 +765,9 @@ static void virtio_gpu_process_cmdq(VirtIOGPU *g)
         /* process command */
         VIRGL(g, virtio_gpu_virgl_process_cmd, virtio_gpu_simple_process_cmd,
               g, cmd);
+        if (cmd->waiting) {
+            break;
+        }
         QTAILQ_REMOVE(&g->cmdq, cmd, next);
         if (virtio_gpu_stats_enabled(g->conf)) {
             g->stats.requests++;

include/hw/virtio/virtio-gpu.h

@@ -76,6 +76,7 @@ struct virtio_gpu_ctrl_command {
     VirtQueue *vq;
     struct virtio_gpu_ctrl_hdr cmd_hdr;
     uint32_t error;
+    bool waiting;
     bool finished;
     QTAILQ_ENTRY(virtio_gpu_ctrl_command) next;
 };
@@ -152,6 +153,7 @@ int virtio_gpu_create_mapping_iov(struct virtio_gpu_resource_attach_backing *ab,
                                   struct virtio_gpu_ctrl_command *cmd,
                                   struct iovec **iov);
 void virtio_gpu_cleanup_mapping_iov(struct iovec *iov, uint32_t count);
+void virtio_gpu_process_cmdq(VirtIOGPU *g);
 
 /* virtio-gpu-3d.c */
 void virtio_gpu_virgl_process_cmd(VirtIOGPU *g,