Re: [PATCH] virtio-ccw: commands on revision-less devices

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

On Fri, Feb 19, 2021 at 12:21:36PM +0100, Cornelia Huck wrote:
> On Tue, 16 Feb 2021 12:18:30 +0100
> Cornelia Huck <cohuck@redhat.com> wrote:
> 
> > The virtio standard specifies that any non-transitional device must
> > reject commands prior to revision setting (which we do) and else
> > assume revision 0 (legacy) if the driver sends a non-revision-setting
> > command first. We neglected to do the latter.
> > 
> > Fortunately, nearly everything worked as intended anyway; the only
> > problem was not properly rejecting revision setting after some other
> > command had been issued. Easy to fix by setting revision to 0 if
> > we see a non-revision command on a legacy-capable revision-less
> > device.
> > 
> > Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> > ---
> >  hw/s390x/virtio-ccw.c | 21 ++++++++++++++-------
> >  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> I now have:
> 
> Author: Cornelia Huck <cohuck@redhat.com>
> Date:   Tue Feb 16 12:18:30 2021 +0100
> 
>     virtio-ccw: commands on revision-less devices
>     
>     The virtio standard specifies that any non-transitional device must
>     reject commands prior to revision setting (which we do). Devices
>     that are transitional need to assume revision 0 (legacy) if the
>     driver sends a non-revision-setting command first in order to
>     support legacy drivers. We neglected to do the latter.
>     
>     Fortunately, nearly everything worked as intended anyway; the only
>     problem was not properly rejecting revision setting after some other
>     command had been issued. Easy to fix by setting revision to 0 if
>     we see a non-revision command on a legacy-capable revision-less
>     device.
>     
>     Found by code inspection, not observed in the wild.
>     
>     Signed-off-by: Cornelia Huck <cohuck@redhat.com>
>     Reviewed-by: Thomas Huth <thuth@redhat.com>
>     Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
>     Acked-by: Halil Pasic <pasic@linux.ibm.com>
>     Message-Id: <20210216111830.1087847-1-cohuck@redhat.com>
> 
> Any objections?

Acked-by: Michael S. Tsirkin <mst@redhat.com>