Re: [virtio-dev] Re: guest / host buffer sharing ...

[Gerd Hoffmann <kraxel@redhat.com>]

  Hi,

> > Of course only virtio drivers would try step (2), other drivers (when
> > sharing buffers between intel gvt device and virtio-gpu for example)
> > would go straight to (3).
> 
> For virtio-gpu as it is today, it's not clear to me that they're
> equivalent. As I read it, the virtio-gpu spec makes a distinction
> between the guest memory and the host resource. If virtio-gpu is
> communicating with non-virtio devices, then obviously you'd just be
> working with guest memory. But if it's communicating with another
> virtio device, then there are potentially distinct guest and host
> buffers that could be used. The spec shouldn't leave any room for
> ambiguity as to how this distinction is handled.

Yep.  It should be the host side buffer.  The whole point is to avoid
the round trip through the guest after all.  Or does someone see a
useful use case for the guest buffer?  If so we might have to add some
way to explicitly specify whenever we want the guest or host buffer.

cheers,
  Gerd