linux-kernel - Re: [PATCH 1/1] vfio-ccw: fence off transport mode

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Message-ID: <20180301160714.22c8113d.cohuck@redhat.com>
Date:   Thu, 1 Mar 2018 16:07:14 +0100
From:   Cornelia Huck <cohuck@...hat.com>
To:     Halil Pasic <pasic@...ux.vnet.ibm.com>
Cc:     Dong Jia Shi <bjsdjshi@...ux.vnet.ibm.com>,
        linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] vfio-ccw: fence off transport mode

On Thu, 1 Mar 2018 15:51:05 +0100
Halil Pasic <pasic@...ux.vnet.ibm.com> wrote:

> On 02/22/2018 04:39 PM, Cornelia Huck wrote:
> > vfio-ccw only supports command mode for channel programs, not transport
> > mode. User space is supposed to already take care of that and pass us
> > command-mode ORBs only, but better make sure and return an error to
> > the caller instead of trying to process tcws as ccws.
> > 
> > Signed-off-by: Cornelia Huck <cohuck@...hat.com>  
> 
> Acked-by: Halil Pasic <pasic@...ux.vnet.ibm.com>

Thanks!

> 
> > ---
> >  drivers/s390/cio/vfio_ccw_fsm.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/s390/cio/vfio_ccw_fsm.c b/drivers/s390/cio/vfio_ccw_fsm.c
> > index c30420c517b1..ff6963ad6e39 100644
> > --- a/drivers/s390/cio/vfio_ccw_fsm.c
> > +++ b/drivers/s390/cio/vfio_ccw_fsm.c
> > @@ -124,6 +124,11 @@ static void fsm_io_request(struct vfio_ccw_private *private,
> >  	if (scsw->cmd.fctl & SCSW_FCTL_START_FUNC) {
> >  		orb = (union orb *)io_region->orb_area;
> > 
> > +		/* Don't try to build a cp if transport mode is specified. */
> > +		if (orb->tm.b) {
> > +			io_region->ret_code = -EOPNOTSUPP;  
> 
> I guess now we communicate this as appropriately as possible.

Yes. We certainly only want to return an error to user space; it is
their responsibility to correctly reflect that to the guest (and even
more their responsibility to not present us with a transport orb in the
first place...)

> 
> > +			goto err_out;
> > +		}
> >  		io_region->ret_code = cp_init(&private->cp, mdev_dev(mdev),
> >  					      orb);
> >  		if (io_region->ret_code)
> >   
>