Re: [RFC] Upstreaming virtio-wayland (or an alternative)

[Boris Brezillon <boris.brezillon@collabora.com>]

On Mon, 24 Feb 2020 14:42:31 +0100
Gerd Hoffmann <kraxel@redhat.com> wrote:

>   Hi,
> 
> > > But let's say we go for a dedicated virtio-device to preserve this
> > > granularity. Should we aim at providing a generic virtio-msg device or
> > > should we keep this so-called wayland-specific virtio device (I'd like
> > > to remind you that it's actually protocol-agnostic)?  
> > 
> > Maybe there's another option (not sure I mentioned it previously):
> > de-correlate the message passing and fd-passing interfaces. If we add a
> > virtio-fd device that takes care of FD passing between guest and host,
> > we can still use a regular vsock to pass messages (can be vhost or
> > !vhost depending on your level of paranoÃa). The wayland proxies would
> > then queue/dequeue messages to/from the vsock and FDs to/from virtio-fd.  
> 
> Hmm, I suspect supporting unix socket passing (by creating a tunnel for
> them) is going to be tricky in with that approach.

Yes, If you want a generic vsock <-> unix proxy, you'll have to
encapsulate the 'message+number of FDs passed' information so the other
end knows how many FDs should be dequeued on the virtio-fd dev. The
other option being to implement proxies that can parse the messages and
extract the 'number of FDs' from there.