Re: [PATCH RFC] virtio-fs: force virtio 1.x usage

[Cornelia Huck <cohuck@redhat.com>]

On Tue, 30 Jun 2020 09:04:38 -0400
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Tue, Jun 30, 2020 at 02:25:04PM +0200, Cornelia Huck wrote:

> > What bothers me most is that you need to explicitly request a device to
> > be modern-only, while that should be the default for any newly added
> > device. Hence the approach with the centralized list of device types
> > mentioned in a parallel thread. The main problem with that is that the
> > proxy device starts getting realized before the virtio device with its
> > id is present... I failed to find a solution so far. But I'd really
> > like an approach that can work for all transports.  
> 
> So how about simply validating that the device is modern only,
> unless it's one of the whitelist?

Who would do the validation, the virtio core? How can it distinguish
between transitional and non-transitional? But maybe I'm just not
getting your idea.

Also, ccw does not currently have a way to explicitly configure a
device non-transitional; the revisions can be used to fence off newer
features, going down to legacy-only, but fencing off older features is
not possible (that is only done by the device, if it has no legacy
support).