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

[Cornelia Huck <cohuck@redhat.com>]

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?