s390/ap: Restrict driver_override versus apmask and aqmask use

Introduce a restriction for the driver_override feature versus apmask
and aqmask:
- driver_override is only allowed when the apmask and aqmask values
  both are default (=0xffff..ffff).
- apmask and aqmask modifications are only allowed when there is no
  driver_override on any AP device active.
So in the end the user is restricted to choose to either use
apmask/apmask to divide the AP devices into host owned and vfio owned
or use the driver_override feature but not mix these two approaches.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

1 files changed, 20 insertions, 3 deletions

diff --git a/drivers/s390/crypto/ap_queue.c b/drivers/s390/crypto/ap_queue.c
index f05ff54f4c4b..4fe443d30f9b 100644
--- a/drivers/s390/crypto/ap_queue.c
+++ b/drivers/s390/crypto/ap_queue.c
@@ -755,13 +755,30 @@ static ssize_t driver_override_store(struct device *dev,
 {
 	struct ap_queue *aq = to_ap_queue(dev);
 	struct ap_device *ap_dev = &aq->ap_dev;
-	int rc;
+	int rc = -EINVAL;
+	bool old_value;
+
+	if (mutex_lock_interruptible(&ap_attr_mutex))
+		return -ERESTARTSYS;
+
+	/* Do not allow driver override if apmask/aqmask is in use */
+	if (ap_apmask_aqmask_in_use)
+		goto out;
 
+	old_value = ap_dev->driver_override ? true : false;
 	rc = driver_set_override(dev, &ap_dev->driver_override, buf, count);
 	if (rc)
-		return rc;
+		goto out;
+	if (old_value && !ap_dev->driver_override)
+		--ap_driver_override_ctr;
+	else if (!old_value && ap_dev->driver_override)
+		++ap_driver_override_ctr;
 
-	return count;
+	rc = count;
+
+out:
+	mutex_unlock(&ap_attr_mutex);
+	return rc;
 }
 
 static DEVICE_ATTR_RW(driver_override);