[PATCH 1/4] s390/vfio-ap: Fix leak of pinned NIB and registered NISC in vfio_ap_irq_enable()

[Anthony Krowiak <akrowiak@linux.ibm.com>]

The vfio_ap_irq_enable() function executes the PQAP(AQIC) instruction to
enable interrupts for an AP queue. A switch statement is used to examine
the status response code returned from the instruction to determine
whether it succeeded or failed and react accordingly. For the default case,
the vfio_ap_irq_disable function is invoked to disable interrupts for the
queue and clean up the AQIC resources (i.e., unpin the NIB and unregister
the NISC). There are a number of problems with this:

1. Neither the q->saved_iova nor q->saved_isc has been set, so the
   AQIC resources - assuming those values have been previously set - will
   be the NIB and NISC resources from a prior call; the NIB and NISC from
   the current call are therefore leaked.

2. Interrupts may never have been enabled. Sending a disable instruction to
   a queue that the hardware just told you is in a bad state (CHECKSTOPPED,
   DECONFIGURED, Q_NOT_AVAIL) is at best wasted work and at worst generates
   a further WARN_ONCE from inside vfio_ap_irq_disable's own default.

3. The hardware just rejected the new ap_aqic() enable attempt with an
   unexpected status. Disabling a previously-working IRQ config - assuming
   that is even possible - as a reaction to a failed enable attempt does
   not make sense; it is actively destructive, tearing down something that
   was working for no valid reason.

The fix is to unregister the NISC and an unpin the NIB in the default case
of the switch statement.

Fixes: ec89b55e3bce7 ("s390: ap: implement PAPQ AQIC interception in kernel")
Cc: stable@vger.kernel.org
Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_ops.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 940c0ff668be..a46bf381ab72 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -503,9 +503,14 @@ static struct ap_queue_status vfio_ap_irq_enable(struct vfio_ap_queue *q,
 		vfio_unpin_pages(&q->matrix_mdev->vdev, nib, 1);
 		break;
 	default:
-		pr_warn("%s: apqn %04x: response: %02x\n", __func__, q->apqn,
-			status.response_code);
-		vfio_ap_irq_disable(q);
+		pr_warn("%s: PQAP(AQIC) failed with response code %02x for apqn %04x\n",
+			__func__, status.response_code, q->apqn);
+		/* We could not modify IRQ settings: clear new configuration */
+		ret = kvm_s390_gisc_unregister(kvm, isc);
+		if (ret)
+			VFIO_AP_DBF_WARN("%s: kvm_s390_gisc_unregister: rc=%d isc=%d, apqn=%#04x\n",
+					 __func__, ret, isc, q->apqn);
+		vfio_unpin_pages(&q->matrix_mdev->vdev, nib, 1);
 		break;
 	}
 
-- 
2.53.0