Re: [PATCH] s390/vfio-ap: handle response code 01 on queue reset

[Tony Krowiak]

On 11/29/23 12:12, Christian Borntraeger wrote:
> Am 29.11.23 um 15:35 schrieb Tony Krowiak:
> > In the current implementation, response code 01 (AP queue number not 
> > valid)
> > is handled as a default case along with other response codes returned 
> > from
> > a queue reset operation that are not handled specifically. Barring a bug,
> > response code 01 will occur only when a queue has been externally removed
> > from the host's AP configuration; nn this case, the queue must
> > be reset by the machine in order to avoid leaking crypto data if/when the
> > queue is returned to the host's configuration. The response code 01 case
> > will be handled specifically by logging a WARN message followed by 
> > cleaning
> > up the IRQ resources.
>
> To me it looks like this can be triggered by the LPAR admin, correct? So it
> is not desireable but possible.
> In that case I prefer to not use WARN, maybe use dev_warn or dev_err 
> instead.
> WARN can be a disruptive event if panic_on_warn is set.

Yes, it can be triggered by the LPAR admin. I can't use dev_warn here 
because we don't have a reference to any device, but I can use pr_warn 
if that suffices.

> > Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
> > ---
> >   drivers/s390/crypto/vfio_ap_ops.c | 31 +++++++++++++++++++++++++++++++
> >   1 file changed, 31 insertions(+)
> >
> > diff --git a/drivers/s390/crypto/vfio_ap_ops.c 
> > b/drivers/s390/crypto/vfio_ap_ops.c
> > index 4db538a55192..91d6334574d8 100644
> > --- a/drivers/s390/crypto/vfio_ap_ops.c
> > +++ b/drivers/s390/crypto/vfio_ap_ops.c
> > @@ -1652,6 +1652,21 @@ static int apq_status_check(int apqn, struct 
> > ap_queue_status *status)
> >            * a value indicating a reset needs to be performed again.
> >            */
> >           return -EAGAIN;
> > +    case AP_RESPONSE_Q_NOT_AVAIL:
> > +        /*
> > +         * This response code indicates the queue is not available.
> > +         * Barring a bug, response code 01 will occur only when a queue
> > +         * has been externally removed from the host's AP configuration;
> > +         * in which case, the queue must be reset by the machine in
> > +         * order to avoid leaking crypto data if/when the queue is
> > +         * returned to the host's configuration. In this case, let's go
> > +         * ahead and log a warning message and return 0 so the AQIC
> > +         * resources get cleaned up by the caller.
> > +         */
> > +        WARN(true,
> > +             "Unable to reset queue %02x.%04x: not in host AP 
> > configuration\n",
> > +             AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
> > +            return 0;
> >       default:
> >           WARN(true,
> >                "failed to verify reset of queue %02x.%04x: TAPQ rc=%u\n",
> > @@ -1736,6 +1751,22 @@ static void vfio_ap_mdev_reset_queue(struct 
> > vfio_ap_queue *q)
> >           q->reset_status.response_code = 0;
> >           vfio_ap_free_aqic_resources(q);
> >           break;
> > +    case AP_RESPONSE_Q_NOT_AVAIL:
> > +        /*
> > +         * This response code indicates the queue is not available.
> > +         * Barring a bug, response code 01 will occur only when a queue
> > +         * has been externally removed from the host's AP configuration;
> > +         * in which case, the queue must be reset by the machine in
> > +         * order to avoid leaking crypto data if/when the queue is
> > +         * returned to the host's configuration. In this case, let's go
> > +         * ahead and log a warning message then clean up the AQIC
> > +         * resources.
> > +         */
> > +        WARN(true,
> > +             "Unable to reset queue %02x.%04x: not in host AP 
> > configuration\n",
> > +             AP_QID_CARD(q->apqn), AP_QID_QUEUE(q->apqn));
> > +        vfio_ap_free_aqic_resources(q);
> > +        break;
> >       default:
> >           WARN(true,
> >                "PQAP/ZAPQ for %02x.%04x failed with invalid rc=%u\n",