Re: [Qemu-devel] [PATCH RFC v4 00/16] qemu: towards virtio-1 host support

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Nov 27, 2014 at 05:28:42PM +0100, Cornelia Huck wrote:
> On Thu, 27 Nov 2014 18:18:25 +0200
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > On Thu, Nov 27, 2014 at 05:06:51PM +0100, Cornelia Huck wrote:
> 
> > > So we should have a per-device callback into the transport layer, say
> > > check_legacy()?
> > 
> > I would just have 2 masks: legacy_features and features.
> 
> But these belong to the device type and the transport just needs to
> trigger usage of the right one, right?

Yes.

> > 
> > > For ccw, this would check for the negotiated revision; for mmio, it
> > > could check a device property configured with the device; and for pci,
> > > whatever the mechanism is there :)
> > > 
> > > A transport not implementing this callback is simply considered
> > > legacy-only.
> > 
> > I dislike callbacks. Let's just give all info to core,
> > and have it DTRT.
> > 
> Have a is_legacy flag in the vdev that is initialized to 1, and
> transports can unset it when the revision is negotiated or during init?

I would say have modern_features, legacy_features, and set host_features
correctly.

-- 
MST