Re: [PATCH 1/2] vfio: ABI for setting mdev display flip eventfd

[Gerd Hoffmann]

On Mon, May 27, 2019 at 05:07:41PM +0800, Zhenyu Wang wrote:
> On 2019.05.27 16:43:11 +0800, Tina Zhang wrote:
> > Add VFIO_DEVICE_SET_GFX_FLIP_EVENTFD ioctl command to set eventfd
> > based signaling mechanism to deliver vGPU framebuffer page flip
> > event to userspace.
> 
> Should we add probe to see if driver can support gfx flip event?

Userspace can simply call VFIO_DEVICE_SET_GFX_FLIP_EVENTFD and see if it
worked.  If so -> use the eventfd.  Otherwise take the fallback path
(timer based polling).  I can't see any advantage a separate feature
probe steps adds.

cheers,
  Gerd