[v7] Add udmabuf misc device

[Gerd Hoffmann]

On Fri, Sep 14, 2018 at 02:00:30PM +0200, Tomeu Vizoso wrote:
> On 09/14/2018 08:37 AM, Gerd Hoffmann wrote:
> >    Hi,
> > 
> > > > Well, no.  This is *not* about 3D, it's about software rendering, for
> > > > example cairo doing its work for gtk apps.  So the workflow would be
> > > > along these lines:
> > > > 
> > > > (1) guest app allocates dumb drm buffer from virtio-gpu, renders to it.
> 
> Why not let clients keep allocating memory for buffers with memfd?
> 
> The guest proxy would then create a virtio-gpu resource to wrap the shm pool
> memory.

Should be workable too, with udmabuf in the guest.  Allocate with memfd,
turn into dmabuf using udmabuf, let the virtio-gpu guest driver import
the thing so you have a virtio-gpu resource handle for it.

I don't see why this is better than using virtio-gpu dumb buffers
directly though.

cheers,
  Gerd