On Tue, Feb 16, 2021 at 12:18:30PM +0100, Cornelia Huck 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 <coh...@redhat.com>
Reviewed-by: Michael S. Tsirkin <m...@redhat.com> Feel free to merge. Curious how was this discovered. > --- > hw/s390x/virtio-ccw.c | 21 ++++++++++++++------- > 1 file changed, 14 insertions(+), 7 deletions(-) > > diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c > index 4582e94ae7dc..06c06056814b 100644 > --- a/hw/s390x/virtio-ccw.c > +++ b/hw/s390x/virtio-ccw.c > @@ -327,13 +327,20 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw) > ccw.cmd_code); > check_len = !((ccw.flags & CCW_FLAG_SLI) && !(ccw.flags & CCW_FLAG_DC)); > > - if (dev->force_revision_1 && dev->revision < 0 && > - ccw.cmd_code != CCW_CMD_SET_VIRTIO_REV) { > - /* > - * virtio-1 drivers must start with negotiating to a revision >= 1, > - * so post a command reject for all other commands > - */ > - return -ENOSYS; > + if (dev->revision < 0 && ccw.cmd_code != CCW_CMD_SET_VIRTIO_REV) { > + if (dev->force_revision_1) { > + /* > + * virtio-1 drivers must start with negotiating to a revision >= > 1, > + * so post a command reject for all other commands > + */ > + return -ENOSYS; > + } else { > + /* > + * If the driver issues any command that is not SET_VIRTIO_REV, > + * we'll have to operate the device in legacy mode. > + */ > + dev->revision = 0; > + } > } > > /* Look at the command. */ > -- > 2.26.2