RE: [PATCH v3 3/5] ui: Create sync objects and fences only for blobs

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

Hi Gerd,

> > >
> > > >      dmabuf->buf.fd = res->dmabuf_fd;
> > > > +    dmabuf->buf.blob = true;
> > >
> > > Do you actually need the 'blob' field?
> > > I think checking 'fd' instead should work too.
> > [Kasireddy, Vivek] I want these changes to be limited to blob resources only as I do not
> > know how they might affect other use-cases or whether they are needed there or not. I
> > don't think I can rely on fd as vfio/display.c also populates the fd field:
> >     dmabuf = g_new0(VFIODMABuf, 1);
> >     dmabuf->dmabuf_id  = plane.dmabuf_id;
> >     dmabuf->buf.width  = plane.width;
> >     dmabuf->buf.height = plane.height;
> >     dmabuf->buf.stride = plane.stride;
> >     dmabuf->buf.fourcc = plane.drm_format;
> >     dmabuf->buf.modifier = plane.drm_format_mod;
> >     dmabuf->buf.fd     = fd;
> >
> > Therefore, I need a way to identify a dmabuf that is associated with blobs vs others.
> 
> And it actually is a dma-buf too (the guest display provided by i915 gvt
> mdev driver).  So fencing that should work, right?
[Kasireddy, Vivek] Well, for virtio-gpu, as you know we are adding a dma fence to
resource_flush to make it wait until it gets signalled by Qemu. We might have to do
to something similar on i915 GVT side but I do not have the hardware to write a patch
and test it out -- as i915 GVT is not supported for > Gen 9 platforms.

> 
> Even if we have to restrict it to some kinds of dma-bufs the field
> should have a more descriptive name like "allow_fences".
[Kasireddy, Vivek] I think limiting this to blobs makes sense at the moment. If need be,
we can extend it to include dma-bufs generated by i915 GVT later. Let me send a
v4 with your suggestion to change the name.

Thanks,
Vivek
> 
> take care,
>   Gerd