Print out error messages when virgl fence creation fails to aid debugging
of the fence-related bugs.

Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Reviewed-by: Yiwei Zhang <zzyiwei@gmail.com>
Tested-by: Yiwei Zhang <zzyiwei@gmail.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
---
 hw/display/virtio-gpu-virgl.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/hw/display/virtio-gpu-virgl.c b/hw/display/virtio-gpu-virgl.c
index 07f6355ad62e..d9704e3574a0 100644
--- a/hw/display/virtio-gpu-virgl.c
+++ b/hw/display/virtio-gpu-virgl.c
@@ -876,6 +876,7 @@ void virtio_gpu_virgl_process_cmd(VirtIOGPU *g,
                                       struct virtio_gpu_ctrl_command *cmd)
 {
     bool cmd_suspended = false;
+    int ret;
 
     VIRTIO_GPU_FILL_CMD(cmd->cmd_hdr);
 
@@ -976,14 +977,30 @@ void virtio_gpu_virgl_process_cmd(VirtIOGPU *g,
     trace_virtio_gpu_fence_ctrl(cmd->cmd_hdr.fence_id, cmd->cmd_hdr.type);
 #if VIRGL_VERSION_MAJOR >= 1
     if (cmd->cmd_hdr.flags & VIRTIO_GPU_FLAG_INFO_RING_IDX) {
-        virgl_renderer_context_create_fence(cmd->cmd_hdr.ctx_id,
-                                            VIRGL_RENDERER_FENCE_FLAG_MERGEABLE,
-                                            cmd->cmd_hdr.ring_idx,
-                                            cmd->cmd_hdr.fence_id);
+        const uint32_t flags = VIRGL_RENDERER_FENCE_FLAG_MERGEABLE;
+
+        ret = virgl_renderer_context_create_fence(cmd->cmd_hdr.ctx_id, flags,
+                                                  cmd->cmd_hdr.ring_idx,
+                                                  cmd->cmd_hdr.fence_id);
+        if (ret) {
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "%s: virgl_renderer_context_create_fence error: %s",
+                          __func__, strerror(-ret));
+        }
         return;
     }
 #endif
-    virgl_renderer_create_fence(cmd->cmd_hdr.fence_id, cmd->cmd_hdr.type);
+
+    /*
+     * Unlike other virglrenderer functions, this one returns a positive
+     * error code.
+     */
+    ret = virgl_renderer_create_fence(cmd->cmd_hdr.fence_id, 0);
+    if (ret) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: virgl_renderer_create_fence error: %s",
+                      __func__, strerror(ret));
+    }
 }
 
 static void virgl_write_fence(void *opaque, uint32_t fence)
-- 
2.51.1