s390/zcrypt: enable AP bus scan without a valid default domain

The AP bus scan is aborted before doing anything worth mentioning if
ap_select_domain() fails, e.g. if the ap_rights.aqm mask is all zeros.
As the result of this the ap bus fails to manage (e.g. create and
register) devices like it is supposed to.

Let us make ap_scan_bus() work even if ap_select_domain() can't select a
default domain. Let's also make ap_select_domain() return void, as there
are no more callers interested in its return value.
Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Reported-by: Michael Mueller <mimu@linux.ibm.com>
Fixes: 7e0bdbe5 "s390/zcrypt: AP bus support for alternate driver(s)"
[freude@linux.ibm.com: title and patch header slightly modified]
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/crypto/ap_bus.c

@@ -1218,11 +1218,10 @@ static struct bus_attribute *const ap_bus_attrs[] = {
 };
 
 /**
- * ap_select_domain(): Select an AP domain.
- *
- * Pick one of the 16 AP domains.
+ * ap_select_domain(): Select an AP domain if possible and we haven't
+ * already done so before.
  */
-static int ap_select_domain(void)
+static void ap_select_domain(void)
 {
 	int count, max_count, best_domain;
 	struct ap_queue_status status;
@@ -1237,7 +1236,7 @@ static int ap_select_domain(void)
 	if (ap_domain_index >= 0) {
 		/* Domain has already been selected. */
 		spin_unlock_bh(&ap_domain_lock);
-		return 0;
+		return;
 	}
 	best_domain = -1;
 	max_count = 0;
@@ -1264,11 +1263,8 @@ static int ap_select_domain(void)
 	if (best_domain >= 0) {
 		ap_domain_index = best_domain;
 		AP_DBF(DBF_DEBUG, "new ap_domain_index=%d\n", ap_domain_index);
-		spin_unlock_bh(&ap_domain_lock);
-		return 0;
 	}
 	spin_unlock_bh(&ap_domain_lock);
-	return -ENODEV;
 }
 
 /*
@@ -1346,8 +1342,7 @@ static void ap_scan_bus(struct work_struct *unused)
 	AP_DBF(DBF_DEBUG, "%s running\n", __func__);
 
 	ap_query_configuration(ap_configuration);
-	if (ap_select_domain() != 0)
-		goto out;
+	ap_select_domain();
 
 	for (id = 0; id < AP_DEVICES; id++) {
 		/* check if device is registered */
@@ -1467,12 +1462,11 @@ static void ap_scan_bus(struct work_struct *unused)
 		}
 	} /* end device loop */
 
-	if (defdomdevs < 1)
+	if (ap_domain_index >= 0 && defdomdevs < 1)
 		AP_DBF(DBF_INFO,
 		       "no queue device with default domain %d available\n",
 		       ap_domain_index);
 
-out:
 	mod_timer(&ap_config_timer, jiffies + ap_config_time * HZ);
 }