Re: guest / host buffer sharing ...

[Stefan Hajnoczi <stefanha@gmail.com>]

On Wed, Nov 6, 2019 at 1:50 PM Gerd Hoffmann <kraxel@redhat.com> wrote:
> > In the graphics buffer sharing use case, how does the other side
> > determine how to interpret this data?
>
> The idea is to have free form properties (name=value, with value being
> a string) for that kind of metadata.
>
> > Shouldn't there be a VIRTIO
> > device spec for the messaging so compatible implementations can be
> > written by others?
>
> Adding a list of common properties to the spec certainly makes sense,
> so everybody uses the same names.  Adding struct-ed properties for
> common use cases might be useful too.

Why not define VIRTIO devices for wayland and friends?

This new device exposes buffer sharing plus properties - effectively a
new device model nested inside VIRTIO.  The VIRTIO device model has
the necessary primitives to solve the buffer sharing problem so I'm
struggling to see the purpose of this new device.

Custom/niche applications that do not wish to standardize their device
type can maintain out-of-tree VIRTIO devices.  Both kernel and
userspace drivers can be written for the device and there is already
VIRTIO driver code that can be reused.  They have access to the full
VIRTIO device model, including feature negotiation and configuration
space.

Stefan