Re: [PATCH v3 2/2] s390/vfio-ap: fix unlinking of queues from the mdev

[Anthony Krowiak]

On 9/13/22 10:07 AM, Halil Pasic wrote:
> On Tue, 23 Aug 2022 11:06:43 -0400
> Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote:
>
> > The vfio_ap_mdev_unlink_adapter and vfio_ap_mdev_unlink_domain functions
> > add the associated vfio_ap_queue objects to the hashtable that links them
> > to the matrix mdev to which their APQN is assigned. In order to unlink
> > them, they must be deleted from the hashtable; if not, they will continue
> > to be reset whenever userspace closes the mdev fd or removes the mdev.
> > This patch fixes that issue.
> I'm not so sure about that!
>
> > Cc: stable@xxxxxxxxxxxxxxx
> > Fixes: 70aeefe574cb ("s390/vfio-ap: reset queues after adapter/domain unassignment")
> > Reported-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
> > Signed-off-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
> > ---
> >   drivers/s390/crypto/vfio_ap_ops.c | 6 ++----
> >   1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> > index ee82207b4e60..2493926b5dfb 100644
> > --- a/drivers/s390/crypto/vfio_ap_ops.c
> > +++ b/drivers/s390/crypto/vfio_ap_ops.c
> > @@ -1049,8 +1049,7 @@ static void vfio_ap_mdev_unlink_adapter(struct ap_matrix_mdev *matrix_mdev,
> >   		if (q && qtable) {
> >   			if (test_bit_inv(apid, matrix_mdev->shadow_apcb.apm) &&
> >   			    test_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm))
> > -				hash_add(qtable->queues, &q->mdev_qnode,
> > -					 q->apqn);
> Careful qtable->queues is not supposed to be the same as
> matrix_mdev->qtable.queues it is rather a function local
> qtable that you use to know which queues were unlinked and
> need resetting.


You are correct. This patch is unnecessary.


> Have a look at vfio_ap_mdev_hot_unplug_adapter()
>
> > +				vfio_ap_unlink_queue_fr_mdev(q);
> IMHO this change is completely bogous. BTW
> vfio_ap_unlink_apqn_fr_mdev() a couple of lines above in the source
> (not seen in diff context) calls vfio_ap_unlink_queue_fr_mdev().


After further review, this patch is not only bogus, it is not necessary.


> >   		}
> >   	}
> >   }
> > @@ -1236,8 +1235,7 @@ static void vfio_ap_mdev_unlink_domain(struct ap_matrix_mdev *matrix_mdev,
> >   		if (q && qtable) {
> >   			if (test_bit_inv(apid, matrix_mdev->shadow_apcb.apm) &&
> >   			    test_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm))
> > -				hash_add(qtable->queues, &q->mdev_qnode,
> > -					 q->apqn);
> > +				vfio_ap_unlink_queue_fr_mdev(q);
> Same as above...
>
> Regards,
> Halil
>
> >   		}
> >   	}
> >   }