Re: [Qemu-devel] [PATCH 3/4] s390/kvm: Add a channel I/O based virtio transport driver.

[Rusty Russell]

On Tue, 14 Aug 2012 13:03:34 +0200, Cornelia Huck <address@hidden> wrote:
> > It would be per-machine; per-device would be a bit crazy.  We'd
> > deprecate the old ring format.
> > 
> > There's been no consistent thread on the ideas for a ring change,
> > unfortunately, but you can find interesting parts here, off this thread:
> > 
> > Message-ID: <address@hidden>
> > Subject: Re: [RFC 7/11] virtio_pci: new, capability-aware driver.
> 
> I've read a bit through this and it looks like this is really virtio-2
> or so. How about discoverability by the guest? Guests will likely have
> to support both formats, and forcing them to look at the feature bits
> for each device in order to figure out the queue format feels wrong if
> it is going to be the same format for the whole machine anyway.

Yes, it needs some out-of-band acknowledgement mechanism by the guest.
Might be worth putting a max version number somewhere, which the guest
writes to acknowledge (ie. currently it would be 1, and the guest would
always write a 1).

Cheers,
Rusty.