[PATCH v4 0/5] virtio-gpu: Add a default synchronization mechanism for blobs

[Vivek Kasireddy <vivek.kasireddy@intel.com>]

When the Guest and Host are using Blob resources, there is a chance
that they may use the underlying storage associated with a Blob at
the same time leading to glitches such as flickering or tearing.
To prevent these from happening, the Host needs to ensure that it
waits until its Blit is completed by the Host GPU before letting
the Guest reuse the Blob.

This should be the default behavior regardless of the type of Guest
that is using Blob resources but would be particularly useful for 
Guests that are using frontbuffer rendering such as Linux with X
or Windows 10, etc.

The way it works is the Guest includes a fence as part of 
resource_flush and waits for it to be signalled. The Host will
queue a repaint request and signal the fence after it completes
waiting on the sync object associated with the Blit.

v2:
- Added more description in the cover letter
- Removed the wait from resource_flush and included it in
  a gl_flushed() callback

v3:
- Instead of explicitly waiting on the sync object and stalling the
  thread, add the relevant fence fd to Qemu's main loop and wait
  for it to be signalled. (suggested by Gerd Hoffmann)

v4:
- Replace the field 'blob' with 'allow_fences' in QemuDmabuf struct.
  (Gerd)

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Dongwon Kim <dongwon.kim@intel.com>
Cc: Tina Zhang <tina.zhang@intel.com>

Vivek Kasireddy (5):
  ui/gtk: Create a common release_dmabuf helper
  ui/egl: Add egl helpers to help with synchronization
  ui: Create sync objects and fences only for blobs
  ui/gtk-egl: Wait for the draw signal for dmabuf blobs
  virtio-gpu: Add gl_flushed callback

 hw/display/virtio-gpu-udmabuf.c |  1 +
 hw/display/virtio-gpu.c         | 32 ++++++++++++++++++++++--
 include/ui/console.h            |  3 +++
 include/ui/egl-helpers.h        |  3 +++
 include/ui/gtk.h                |  5 ++--
 ui/egl-helpers.c                | 26 ++++++++++++++++++++
 ui/gtk-egl.c                    | 43 +++++++++++++++++++++++++++------
 ui/gtk-gl-area.c                | 20 +++++++++++++++
 ui/gtk.c                        | 26 ++++++++++++++++++--
 9 files changed, 145 insertions(+), 14 deletions(-)

-- 
2.30.2