On Mon, 13 Jul 2015 11:56:51 +0200
Kevin Wolf <kw...@redhat.com> wrote:
> Am 13.07.2015 um 11:00 hat Jason Wang geschrieben:
> >
> >
> > On 07/13/2015 03:46 PM, Michael S. Tsirkin wrote:
> > > On Mon, Jul 13, 2015 at 01:46:48PM +0800, Jason Wang wrote:
> > >> VIRTIO_BLK_F_SCSI was no longer supported in 1.0. So disable it.
> > >>
> > >> Cc: Stefan Hajnoczi <stefa...@redhat.com>
> > >> Cc: Kevin Wolf <kw...@redhat.com>
> > >> Cc: qemu-bl...@nongnu.org
> > >> Signed-off-by: Jason Wang <jasow...@redhat.com>
> > > Interesting, I noticed we have a field scsi - see
> > > commit 1ba1f2e319afdcb485963cd3f426fdffd1b725f2
> > > Author: Paolo Bonzini <pbonz...@redhat.com>
> > > Date: Fri Dec 23 15:39:03 2011 +0100
> > >
> > > virtio-blk: refuse SG_IO requests with scsi=off
> > >
> > > but it doesn't seem to be propagated to guest features in
> > > any way.
> > >
> > > Maybe we should fix that, making that flag AutoOnOff?
> >
> > Looks ok but auto may need some compat work since default is true.
> >
> > > Then, if user explicitly requested scsi=on with a modern
> > > interface then we can error out cleanly.
> > >
> > > Given scsi flag is currently ignored, I think
> > > this can be a patch on top.
> >
> > Looks like virtio_blk_handle_scsi_req() check this:
> >
> > if (!blk->conf.scsi) {
> > status = VIRTIO_BLK_S_UNSUPP;
> > goto fail;
> > }
>
> So we should be checking the same condition for the feature flag and
> error out in the init function if we have a VERSION_1 device and
> blk->conf.scsi is set.
Hm, I wonder how this plays with transports that want to make the
virtio-1 vs. legacy decision post-init? For virtio-ccw, I basically
only want to offer VERSION_1 if the driver negotiated revision >= 1.
I'd need to check for !scsi as well before I can add this feature bit
then? Have the init function set a blocker for VERSION_1 so that the
driver may only negotiate revision 0?
