1 files changed, 331 insertions, 166 deletions

diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index f46dd6abac..898865be0d 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -38,13 +38,16 @@
 #include <linux/debugfs.h>
 #include <linux/ctype.h>
 #include <linux/module.h>
+#include <asm/uv.h>
+#include <asm/chsc.h>
 
 #include "ap_bus.h"
 #include "ap_debug.h"
 
-/*
- * Module parameters; note though this file itself isn't modular.
- */
+MODULE_AUTHOR("IBM Corporation");
+MODULE_DESCRIPTION("Adjunct Processor Bus driver");
+MODULE_LICENSE("GPL");
+
 int ap_domain_index = -1;	/* Adjunct Processor Domain Index */
 static DEFINE_SPINLOCK(ap_domain_lock);
 module_param_named(domain, ap_domain_index, int, 0440);
@@ -83,17 +86,15 @@ EXPORT_SYMBOL(ap_perms);
 DEFINE_MUTEX(ap_perms_mutex);
 EXPORT_SYMBOL(ap_perms_mutex);
 
-/* # of bus scans since init */
-static atomic64_t ap_scan_bus_count;
-
 /* # of bindings complete since init */
 static atomic64_t ap_bindings_complete_count = ATOMIC64_INIT(0);
 
-/* completion for initial APQN bindings complete */
-static DECLARE_COMPLETION(ap_init_apqn_bindings_complete);
+/* completion for APQN bindings complete */
+static DECLARE_COMPLETION(ap_apqn_bindings_complete);
 
-static struct ap_config_info *ap_qci_info;
-static struct ap_config_info *ap_qci_info_old;
+static struct ap_config_info qci[2];
+static struct ap_config_info *const ap_qci_info = &qci[0];
+static struct ap_config_info *const ap_qci_info_old = &qci[1];
 
 /*
  * AP bus related debug feature things.
@@ -101,12 +102,16 @@ static struct ap_config_info *ap_qci_info_old;
 debug_info_t *ap_dbf_info;
 
 /*
- * Workqueue timer for bus rescan.
+ * AP bus rescan related things.
  */
-static struct timer_list ap_config_timer;
-static int ap_config_time = AP_CONFIG_TIME;
-static void ap_scan_bus(struct work_struct *);
-static DECLARE_WORK(ap_scan_work, ap_scan_bus);
+static bool ap_scan_bus(void);
+static bool ap_scan_bus_result; /* result of last ap_scan_bus() */
+static DEFINE_MUTEX(ap_scan_bus_mutex); /* mutex ap_scan_bus() invocations */
+static atomic64_t ap_scan_bus_count; /* counter ap_scan_bus() invocations */
+static int ap_scan_bus_time = AP_CONFIG_TIME;
+static struct timer_list ap_scan_bus_timer;
+static void ap_scan_bus_wq_callback(struct work_struct *);
+static DECLARE_WORK(ap_scan_bus_work, ap_scan_bus_wq_callback);
 
 /*
  * Tasklet & timer for AP request polling and interrupts
@@ -135,7 +140,7 @@ static int ap_max_domain_id = 15;
 /* Maximum adapter id, if not given via qci */
 static int ap_max_adapter_id = 63;
 
-static struct bus_type ap_bus_type;
+static const struct bus_type ap_bus_type;
 
 /* Adapter interrupt definitions */
 static void ap_interrupt_handler(struct airq_struct *airq,
@@ -201,9 +206,7 @@ static int ap_apft_available(void)
  */
 static inline int ap_qact_available(void)
 {
-	if (ap_qci_info)
-		return ap_qci_info->qact;
-	return 0;
+	return ap_qci_info->qact;
 }
 
 /*
@@ -213,9 +216,7 @@ static inline int ap_qact_available(void)
  */
 int ap_sb_available(void)
 {
-	if (ap_qci_info)
-		return ap_qci_info->apsb;
-	return 0;
+	return ap_qci_info->apsb;
 }
 
 /*
@@ -227,23 +228,6 @@ bool ap_is_se_guest(void)
 }
 EXPORT_SYMBOL(ap_is_se_guest);
 
-/*
- * ap_fetch_qci_info(): Fetch cryptographic config info
- *
- * Returns the ap configuration info fetched via PQAP(QCI).
- * On success 0 is returned, on failure a negative errno
- * is returned, e.g. if the PQAP(QCI) instruction is not
- * available, the return value will be -EOPNOTSUPP.
- */
-static inline int ap_fetch_qci_info(struct ap_config_info *info)
-{
-	if (!ap_qci_available())
-		return -EOPNOTSUPP;
-	if (!info)
-		return -EINVAL;
-	return ap_qci(info);
-}
-
 /**
  * ap_init_qci_info(): Allocate and query qci config info.
  * Does also update the static variables ap_max_domain_id
@@ -251,27 +235,12 @@ static inline int ap_fetch_qci_info(struct ap_config_info *info)
  */
 static void __init ap_init_qci_info(void)
 {
-	if (!ap_qci_available()) {
+	if (!ap_qci_available() ||
+	    ap_qci(ap_qci_info)) {
 		AP_DBF_INFO("%s QCI not supported\n", __func__);
 		return;
 	}
-
-	ap_qci_info = kzalloc(sizeof(*ap_qci_info), GFP_KERNEL);
-	if (!ap_qci_info)
-		return;
-	ap_qci_info_old = kzalloc(sizeof(*ap_qci_info_old), GFP_KERNEL);
-	if (!ap_qci_info_old) {
-		kfree(ap_qci_info);
-		ap_qci_info = NULL;
-		return;
-	}
-	if (ap_fetch_qci_info(ap_qci_info) != 0) {
-		kfree(ap_qci_info);
-		kfree(ap_qci_info_old);
-		ap_qci_info = NULL;
-		ap_qci_info_old = NULL;
-		return;
-	}
+	memcpy(ap_qci_info_old, ap_qci_info, sizeof(*ap_qci_info));
 	AP_DBF_INFO("%s successful fetched initial qci info\n", __func__);
 
 	if (ap_qci_info->apxa) {
@@ -286,8 +255,6 @@ static void __init ap_init_qci_info(void)
 				    __func__, ap_max_domain_id);
 		}
 	}
-
-	memcpy(ap_qci_info_old, ap_qci_info, sizeof(*ap_qci_info));
 }
 
 /*
@@ -310,7 +277,7 @@ static inline int ap_test_config_card_id(unsigned int id)
 {
 	if (id > ap_max_adapter_id)
 		return 0;
-	if (ap_qci_info)
+	if (ap_qci_info->flags)
 		return ap_test_config(ap_qci_info->apm, id);
 	return 1;
 }
@@ -327,7 +294,7 @@ int ap_test_config_usage_domain(unsigned int domain)
 {
 	if (domain > ap_max_domain_id)
 		return 0;
-	if (ap_qci_info)
+	if (ap_qci_info->flags)
 		return ap_test_config(ap_qci_info->aqm, domain);
 	return 1;
 }
@@ -753,7 +720,7 @@ static void ap_calc_bound_apqns(unsigned int *apqns, unsigned int *bound)
 }
 
 /*
- * After initial ap bus scan do check if all existing APQNs are
+ * After ap bus scan do check if all existing APQNs are
  * bound to device drivers.
  */
 static void ap_check_bindings_complete(void)
@@ -763,11 +730,11 @@ static void ap_check_bindings_complete(void)
 	if (atomic64_read(&ap_scan_bus_count) >= 1) {
 		ap_calc_bound_apqns(&apqns, &bound);
 		if (bound == apqns) {
-			if (!completion_done(&ap_init_apqn_bindings_complete)) {
-				complete_all(&ap_init_apqn_bindings_complete);
-				AP_DBF_INFO("%s complete\n", __func__);
+			if (!completion_done(&ap_apqn_bindings_complete)) {
+				complete_all(&ap_apqn_bindings_complete);
+				ap_send_bindings_complete_uevent();
+				pr_debug("%s all apqn bindings complete\n", __func__);
 			}
-			ap_send_bindings_complete_uevent();
 		}
 	}
 }
@@ -782,27 +749,29 @@ static void ap_check_bindings_complete(void)
  * -ETIME is returned. On failures negative return values are
  * returned to the caller.
  */
-int ap_wait_init_apqn_bindings_complete(unsigned long timeout)
+int ap_wait_apqn_bindings_complete(unsigned long timeout)
 {
+	int rc = 0;
 	long l;
 
-	if (completion_done(&ap_init_apqn_bindings_complete))
+	if (completion_done(&ap_apqn_bindings_complete))
 		return 0;
 
 	if (timeout)
 		l = wait_for_completion_interruptible_timeout(
-			&ap_init_apqn_bindings_complete, timeout);
+			&ap_apqn_bindings_complete, timeout);
 	else
 		l = wait_for_completion_interruptible(
-			&ap_init_apqn_bindings_complete);
+			&ap_apqn_bindings_complete);
 	if (l < 0)
-		return l == -ERESTARTSYS ? -EINTR : l;
+		rc = l == -ERESTARTSYS ? -EINTR : l;
 	else if (l == 0 && timeout)
-		return -ETIME;
+		rc = -ETIME;
 
-	return 0;
+	pr_debug("%s rc=%d\n", __func__, rc);
+	return rc;
 }
-EXPORT_SYMBOL(ap_wait_init_apqn_bindings_complete);
+EXPORT_SYMBOL(ap_wait_apqn_bindings_complete);
 
 static int __ap_queue_devices_with_id_unregister(struct device *dev, void *data)
 {
@@ -826,8 +795,8 @@ static int __ap_revise_reserved(struct device *dev, void *dummy)
 		drvres = to_ap_drv(dev->driver)->flags
 			& AP_DRIVER_FLAG_DEFAULT;
 		if (!!devres != !!drvres) {
-			AP_DBF_DBG("%s reprobing queue=%02x.%04x\n",
-				   __func__, card, queue);
+			pr_debug("%s reprobing queue=%02x.%04x\n",
+				 __func__, card, queue);
 			rc = device_reprobe(dev);
 			if (rc)
 				AP_DBF_WARN("%s reprobing queue=%02x.%04x failed\n",
@@ -925,6 +894,12 @@ static int ap_device_probe(struct device *dev)
 			goto out;
 	}
 
+	/*
+	 * Rearm the bindings complete completion to trigger
+	 * bindings complete when all devices are bound again
+	 */
+	reinit_completion(&ap_apqn_bindings_complete);
+
 	/* Add queue/card to list of active queues/cards */
 	spin_lock_bh(&ap_queues_lock);
 	if (is_queue_dev(dev))
@@ -939,8 +914,6 @@ static int ap_device_probe(struct device *dev)
 		if (is_queue_dev(dev))
 			hash_del(&to_ap_queue(dev)->hnode);
 		spin_unlock_bh(&ap_queues_lock);
-	} else {
-		ap_check_bindings_complete();
 	}
 
 out:
@@ -1012,38 +985,71 @@ void ap_driver_unregister(struct ap_driver *ap_drv)
 }
 EXPORT_SYMBOL(ap_driver_unregister);
 
-void ap_bus_force_rescan(void)
+/*
+ * Enforce a synchronous AP bus rescan.
+ * Returns true if the bus scan finds a change in the AP configuration
+ * and AP devices have been added or deleted when this function returns.
+ */
+bool ap_bus_force_rescan(void)
 {
+	unsigned long scan_counter = atomic64_read(&ap_scan_bus_count);
+	bool rc = false;
+
+	pr_debug(">%s scan counter=%lu\n", __func__, scan_counter);
+
 	/* Only trigger AP bus scans after the initial scan is done */
-	if (atomic64_read(&ap_scan_bus_count) <= 0)
-		return;
+	if (scan_counter <= 0)
+		goto out;
+
+	/* Try to acquire the AP scan bus mutex */
+	if (mutex_trylock(&ap_scan_bus_mutex)) {
+		/* mutex acquired, run the AP bus scan */
+		ap_scan_bus_result = ap_scan_bus();
+		rc = ap_scan_bus_result;
+		mutex_unlock(&ap_scan_bus_mutex);
+		goto out;
+	}
 
-	/* processing a asynchronous bus rescan */
-	del_timer(&ap_config_timer);
-	queue_work(system_long_wq, &ap_scan_work);
-	flush_work(&ap_scan_work);
+	/*
+	 * Mutex acquire failed. So there is currently another task
+	 * already running the AP bus scan. Then let's simple wait
+	 * for the lock which means the other task has finished and
+	 * stored the result in ap_scan_bus_result.
+	 */
+	if (mutex_lock_interruptible(&ap_scan_bus_mutex)) {
+		/* some error occurred, ignore and go out */
+		goto out;
+	}
+	rc = ap_scan_bus_result;
+	mutex_unlock(&ap_scan_bus_mutex);
+
+out:
+	pr_debug("%s rc=%d\n", __func__, rc);
+	return rc;
 }
 EXPORT_SYMBOL(ap_bus_force_rescan);
 
 /*
  * A config change has happened, force an ap bus rescan.
  */
-void ap_bus_cfg_chg(void)
+static int ap_bus_cfg_chg(struct notifier_block *nb,
+			  unsigned long action, void *data)
 {
-	AP_DBF_DBG("%s config change, forcing bus rescan\n", __func__);
+	if (action != CHSC_NOTIFY_AP_CFG)
+		return NOTIFY_DONE;
+
+	pr_debug("%s config change, forcing bus rescan\n", __func__);
 
 	ap_bus_force_rescan();
+
+	return NOTIFY_OK;
 }
 
-/*
- * hex2bitmap() - parse hex mask string and set bitmap.
- * Valid strings are "0x012345678" with at least one valid hex number.
- * Rest of the bitmap to the right is padded with 0. No spaces allowed
- * within the string, the leading 0x may be omitted.
- * Returns the bitmask with exactly the bits set as given by the hex
- * string (both in big endian order).
- */
-static int hex2bitmap(const char *str, unsigned long *bitmap, int bits)
+static struct notifier_block ap_bus_nb = {
+	.notifier_call = ap_bus_cfg_chg,
+};
+
+int ap_hex2bitmap(const char *str, unsigned long *bitmap, int bits)
 {
 	int i, n, b;
 
@@ -1070,6 +1076,7 @@ static int hex2bitmap(const char *str, unsigned long *bitmap, int bits)
 		return -EINVAL;
 	return 0;
 }
+EXPORT_SYMBOL(ap_hex2bitmap);
 
 /*
  * modify_bitmap() - parse bitmask argument and modify an existing
@@ -1090,7 +1097,7 @@ static int hex2bitmap(const char *str, unsigned long *bitmap, int bits)
  */
 static int modify_bitmap(const char *str, unsigned long *bitmap, int bits)
 {
-	int a, i, z;
+	unsigned long a, i, z;
 	char *np, sign;
 
 	/* bits needs to be a multiple of 8 */
@@ -1135,7 +1142,7 @@ static int ap_parse_bitmap_str(const char *str, unsigned long *bitmap, int bits,
 		rc = modify_bitmap(str, newmap, bits);
 	} else {
 		memset(newmap, 0, size);
-		rc = hex2bitmap(str, newmap, bits);
+		rc = ap_hex2bitmap(str, newmap, bits);
 	}
 	return rc;
 }
@@ -1201,7 +1208,7 @@ static BUS_ATTR_RW(ap_domain);
 
 static ssize_t ap_control_domain_mask_show(const struct bus_type *bus, char *buf)
 {
-	if (!ap_qci_info)	/* QCI not supported */
+	if (!ap_qci_info->flags)	/* QCI not supported */
 		return sysfs_emit(buf, "not supported\n");
 
 	return sysfs_emit(buf, "0x%08x%08x%08x%08x%08x%08x%08x%08x\n",
@@ -1215,7 +1222,7 @@ static BUS_ATTR_RO(ap_control_domain_mask);
 
 static ssize_t ap_usage_domain_mask_show(const struct bus_type *bus, char *buf)
 {
-	if (!ap_qci_info)	/* QCI not supported */
+	if (!ap_qci_info->flags)	/* QCI not supported */
 		return sysfs_emit(buf, "not supported\n");
 
 	return sysfs_emit(buf, "0x%08x%08x%08x%08x%08x%08x%08x%08x\n",
@@ -1229,7 +1236,7 @@ static BUS_ATTR_RO(ap_usage_domain_mask);
 
 static ssize_t ap_adapter_mask_show(const struct bus_type *bus, char *buf)
 {
-	if (!ap_qci_info)	/* QCI not supported */
+	if (!ap_qci_info->flags)	/* QCI not supported */
 		return sysfs_emit(buf, "not supported\n");
 
 	return sysfs_emit(buf, "0x%08x%08x%08x%08x%08x%08x%08x%08x\n",
@@ -1250,7 +1257,7 @@ static BUS_ATTR_RO(ap_interrupts);
 
 static ssize_t config_time_show(const struct bus_type *bus, char *buf)
 {
-	return sysfs_emit(buf, "%d\n", ap_config_time);
+	return sysfs_emit(buf, "%d\n", ap_scan_bus_time);
 }
 
 static ssize_t config_time_store(const struct bus_type *bus,
@@ -1260,8 +1267,8 @@ static ssize_t config_time_store(const struct bus_type *bus,
 
 	if (sscanf(buf, "%d\n", &time) != 1 || time < 5 || time > 120)
 		return -EINVAL;
-	ap_config_time = time;
-	mod_timer(&ap_config_timer, jiffies + ap_config_time * HZ);
+	ap_scan_bus_time = time;
+	mod_timer(&ap_scan_bus_timer, jiffies + ap_scan_bus_time * HZ);
 	return count;
 }
 
@@ -1562,7 +1569,7 @@ static ssize_t features_show(const struct bus_type *bus, char *buf)
 {
 	int n = 0;
 
-	if (!ap_qci_info)	/* QCI not supported */
+	if (!ap_qci_info->flags)	/* QCI not supported */
 		return sysfs_emit(buf, "-\n");
 
 	if (ap_qci_info->apsc)
@@ -1603,7 +1610,7 @@ static struct attribute *ap_bus_attrs[] = {
 };
 ATTRIBUTE_GROUPS(ap_bus);
 
-static struct bus_type ap_bus_type = {
+static const struct bus_type ap_bus_type = {
 	.name = "ap",
 	.bus_groups = ap_bus_groups,
 	.match = &ap_bus_match,
@@ -1888,8 +1895,8 @@ static inline void ap_scan_domains(struct ap_card *ac)
 				aq->last_err_rc = AP_RESPONSE_CHECKSTOPPED;
 			}
 			spin_unlock_bh(&aq->lock);
-			AP_DBF_DBG("%s(%d,%d) queue dev checkstop on\n",
-				   __func__, ac->id, dom);
+			pr_debug("%s(%d,%d) queue dev checkstop on\n",
+				 __func__, ac->id, dom);
 			/* 'receive' pending messages with -EAGAIN */
 			ap_flush_queue(aq);
 			goto put_dev_and_continue;
@@ -1899,8 +1906,8 @@ static inline void ap_scan_domains(struct ap_card *ac)
 			if (aq->dev_state > AP_DEV_STATE_UNINITIATED)
 				_ap_queue_init_state(aq);
 			spin_unlock_bh(&aq->lock);
-			AP_DBF_DBG("%s(%d,%d) queue dev checkstop off\n",
-				   __func__, ac->id, dom);
+			pr_debug("%s(%d,%d) queue dev checkstop off\n",
+				 __func__, ac->id, dom);
 			goto put_dev_and_continue;
 		}
 		/* config state change */
@@ -1912,8 +1919,8 @@ static inline void ap_scan_domains(struct ap_card *ac)
 				aq->last_err_rc = AP_RESPONSE_DECONFIGURED;
 			}
 			spin_unlock_bh(&aq->lock);
-			AP_DBF_DBG("%s(%d,%d) queue dev config off\n",
-				   __func__, ac->id, dom);
+			pr_debug("%s(%d,%d) queue dev config off\n",
+				 __func__, ac->id, dom);
 			ap_send_config_uevent(&aq->ap_dev, aq->config);
 			/* 'receive' pending messages with -EAGAIN */
 			ap_flush_queue(aq);
@@ -1924,8 +1931,8 @@ static inline void ap_scan_domains(struct ap_card *ac)
 			if (aq->dev_state > AP_DEV_STATE_UNINITIATED)
 				_ap_queue_init_state(aq);
 			spin_unlock_bh(&aq->lock);
-			AP_DBF_DBG("%s(%d,%d) queue dev config on\n",
-				   __func__, ac->id, dom);
+			pr_debug("%s(%d,%d) queue dev config on\n",
+				 __func__, ac->id, dom);
 			ap_send_config_uevent(&aq->ap_dev, aq->config);
 			goto put_dev_and_continue;
 		}
@@ -1997,8 +2004,8 @@ static inline void ap_scan_adapter(int ap)
 			ap_scan_rm_card_dev_and_queue_devs(ac);
 			put_device(dev);
 		} else {
-			AP_DBF_DBG("%s(%d) no type info (no APQN found), ignored\n",
-				   __func__, ap);
+			pr_debug("%s(%d) no type info (no APQN found), ignored\n",
+				 __func__, ap);
 		}
 		return;
 	}
@@ -2010,8 +2017,8 @@ static inline void ap_scan_adapter(int ap)
 			ap_scan_rm_card_dev_and_queue_devs(ac);
 			put_device(dev);
 		} else {
-			AP_DBF_DBG("%s(%d) no valid type (0) info, ignored\n",
-				   __func__, ap);
+			pr_debug("%s(%d) no valid type (0) info, ignored\n",
+				 __func__, ap);
 		}
 		return;
 	}
@@ -2125,33 +2132,90 @@ static inline void ap_scan_adapter(int ap)
  */
 static bool ap_get_configuration(void)
 {
-	if (!ap_qci_info)	/* QCI not supported */
+	if (!ap_qci_info->flags)	/* QCI not supported */
 		return false;
 
 	memcpy(ap_qci_info_old, ap_qci_info, sizeof(*ap_qci_info));
-	ap_fetch_qci_info(ap_qci_info);
+	ap_qci(ap_qci_info);
 
 	return memcmp(ap_qci_info, ap_qci_info_old,
 		      sizeof(struct ap_config_info)) != 0;
 }
 
+/*
+ * ap_config_has_new_aps - Check current against old qci info if
+ * new adapters have appeared. Returns true if at least one new
+ * adapter in the apm mask is showing up. Existing adapters or
+ * receding adapters are not counted.
+ */
+static bool ap_config_has_new_aps(void)
+{
+
+	unsigned long m[BITS_TO_LONGS(AP_DEVICES)];
+
+	if (!ap_qci_info->flags)
+		return false;
+
+	bitmap_andnot(m, (unsigned long *)ap_qci_info->apm,
+		      (unsigned long *)ap_qci_info_old->apm, AP_DEVICES);
+	if (!bitmap_empty(m, AP_DEVICES))
+		return true;
+
+	return false;
+}
+
+/*
+ * ap_config_has_new_doms - Check current against old qci info if
+ * new (usage) domains have appeared. Returns true if at least one
+ * new domain in the aqm mask is showing up. Existing domains or
+ * receding domains are not counted.
+ */
+static bool ap_config_has_new_doms(void)
+{
+	unsigned long m[BITS_TO_LONGS(AP_DOMAINS)];
+
+	if (!ap_qci_info->flags)
+		return false;
+
+	bitmap_andnot(m, (unsigned long *)ap_qci_info->aqm,
+		      (unsigned long *)ap_qci_info_old->aqm, AP_DOMAINS);
+	if (!bitmap_empty(m, AP_DOMAINS))
+		return true;
+
+	return false;
+}
+
 /**
  * ap_scan_bus(): Scan the AP bus for new devices
- * Runs periodically, workqueue timer (ap_config_time)
- * @unused: Unused pointer.
+ * Always run under mutex ap_scan_bus_mutex protection
+ * which needs to get locked/unlocked by the caller!
+ * Returns true if any config change has been detected
+ * during the scan, otherwise false.
  */
-static void ap_scan_bus(struct work_struct *unused)
+static bool ap_scan_bus(void)
 {
-	int ap, config_changed = 0;
+	bool config_changed;
+	int ap;
+
+	pr_debug(">%s\n", __func__);
 
-	/* config change notify */
+	/* (re-)fetch configuration via QCI */
 	config_changed = ap_get_configuration();
-	if (config_changed)
+	if (config_changed) {
+		if (ap_config_has_new_aps() || ap_config_has_new_doms()) {
+			/*
+			 * Appearance of new adapters and/or domains need to
+			 * build new ap devices which need to get bound to an
+			 * device driver. Thus reset the APQN bindings complete
+			 * completion.
+			 */
+			reinit_completion(&ap_apqn_bindings_complete);
+		}
+		/* post a config change notify */
 		notify_config_changed();
+	}
 	ap_select_domain();
 
-	AP_DBF_DBG("%s running\n", __func__);
-
 	/* loop over all possible adapters */
 	for (ap = 0; ap <= ap_max_adapter_id; ap++)
 		ap_scan_adapter(ap);
@@ -2174,23 +2238,131 @@ static void ap_scan_bus(struct work_struct *unused)
 	}
 
 	if (atomic64_inc_return(&ap_scan_bus_count) == 1) {
-		AP_DBF_DBG("%s init scan complete\n", __func__);
+		pr_debug("%s init scan complete\n", __func__);
 		ap_send_init_scan_done_uevent();
-		ap_check_bindings_complete();
 	}
 
-	mod_timer(&ap_config_timer, jiffies + ap_config_time * HZ);
+	ap_check_bindings_complete();
+
+	mod_timer(&ap_scan_bus_timer, jiffies + ap_scan_bus_time * HZ);
+
+	pr_debug("<%s config_changed=%d\n", __func__, config_changed);
+
+	return config_changed;
 }
 
-static void ap_config_timeout(struct timer_list *unused)
+/*
+ * Callback for the ap_scan_bus_timer
+ * Runs periodically, workqueue timer (ap_scan_bus_time)
+ */
+static void ap_scan_bus_timer_callback(struct timer_list *unused)
 {
-	queue_work(system_long_wq, &ap_scan_work);
+	/*
+	 * schedule work into the system long wq which when
+	 * the work is finally executed, calls the AP bus scan.
+	 */
+	queue_work(system_long_wq, &ap_scan_bus_work);
 }
 
-static int __init ap_debug_init(void)
+/*
+ * Callback for the ap_scan_bus_work
+ */
+static void ap_scan_bus_wq_callback(struct work_struct *unused)
+{
+	/*
+	 * Try to invoke an ap_scan_bus(). If the mutex acquisition
+	 * fails there is currently another task already running the
+	 * AP scan bus and there is no need to wait and re-trigger the
+	 * scan again. Please note at the end of the scan bus function
+	 * the AP scan bus timer is re-armed which triggers then the
+	 * ap_scan_bus_timer_callback which enqueues a work into the
+	 * system_long_wq which invokes this function here again.
+	 */
+	if (mutex_trylock(&ap_scan_bus_mutex)) {
+		ap_scan_bus_result = ap_scan_bus();
+		mutex_unlock(&ap_scan_bus_mutex);
+	}
+}
+
+static inline void __exit ap_async_exit(void)
+{
+	if (ap_thread_flag)
+		ap_poll_thread_stop();
+	chsc_notifier_unregister(&ap_bus_nb);
+	cancel_work(&ap_scan_bus_work);
+	hrtimer_cancel(&ap_poll_timer);
+	timer_delete(&ap_scan_bus_timer);
+}
+
+static inline int __init ap_async_init(void)
+{
+	int rc;
+
+	/* Setup the AP bus rescan timer. */
+	timer_setup(&ap_scan_bus_timer, ap_scan_bus_timer_callback, 0);
+
+	/*
+	 * Setup the high resolution poll timer.
+	 * If we are running under z/VM adjust polling to z/VM polling rate.
+	 */
+	if (MACHINE_IS_VM)
+		poll_high_timeout = 1500000;
+	hrtimer_init(&ap_poll_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+	ap_poll_timer.function = ap_poll_timeout;
+
+	queue_work(system_long_wq, &ap_scan_bus_work);
+
+	rc = chsc_notifier_register(&ap_bus_nb);
+	if (rc)
+		goto out;
+
+	/* Start the low priority AP bus poll thread. */
+	if (!ap_thread_flag)
+		return 0;
+
+	rc = ap_poll_thread_start();
+	if (rc)
+		goto out_notifier;
+
+	return 0;
+
+out_notifier:
+	chsc_notifier_unregister(&ap_bus_nb);
+out:
+	cancel_work(&ap_scan_bus_work);
+	hrtimer_cancel(&ap_poll_timer);
+	timer_delete(&ap_scan_bus_timer);
+	return rc;
+}
+
+static inline void ap_irq_exit(void)
+{
+	if (ap_irq_flag)
+		unregister_adapter_interrupt(&ap_airq);
+}
+
+static inline int __init ap_irq_init(void)
+{
+	int rc;
+
+	if (!ap_interrupts_available() || !ap_useirq)
+		return 0;
+
+	rc = register_adapter_interrupt(&ap_airq);
+	ap_irq_flag = (rc == 0);
+
+	return rc;
+}
+
+static inline void ap_debug_exit(void)
+{
+	debug_unregister(ap_dbf_info);
+}
+
+static inline int __init ap_debug_init(void)
 {
 	ap_dbf_info = debug_register("ap", 2, 1,
-				     DBF_MAX_SPRINTF_ARGS * sizeof(long));
+				     AP_DBF_MAX_SPRINTF_ARGS * sizeof(long));
 	debug_register_view(ap_dbf_info, &debug_sprintf_view);
 	debug_set_level(ap_dbf_info, DBF_ERR);
 
@@ -2255,12 +2427,6 @@ static int __init ap_module_init(void)
 		ap_domain_index = -1;
 	}
 
-	/* enable interrupts if available */
-	if (ap_interrupts_available() && ap_useirq) {
-		rc = register_adapter_interrupt(&ap_airq);
-		ap_irq_flag = (rc == 0);
-	}
-
 	/* Create /sys/bus/ap. */
 	rc = bus_register(&ap_bus_type);
 	if (rc)
@@ -2273,38 +2439,37 @@ static int __init ap_module_init(void)
 		goto out_bus;
 	ap_root_device->bus = &ap_bus_type;
 
-	/* Setup the AP bus rescan timer. */
-	timer_setup(&ap_config_timer, ap_config_timeout, 0);
-
-	/*
-	 * Setup the high resolution poll timer.
-	 * If we are running under z/VM adjust polling to z/VM polling rate.
-	 */
-	if (MACHINE_IS_VM)
-		poll_high_timeout = 1500000;
-	hrtimer_init(&ap_poll_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
-	ap_poll_timer.function = ap_poll_timeout;
-
-	/* Start the low priority AP bus poll thread. */
-	if (ap_thread_flag) {
-		rc = ap_poll_thread_start();
-		if (rc)
-			goto out_work;
-	}
+	/* enable interrupts if available */
+	rc = ap_irq_init();
+	if (rc)
+		goto out_device;
 
-	queue_work(system_long_wq, &ap_scan_work);
+	/* Setup asynchronous work (timers, workqueue, etc). */
+	rc = ap_async_init();
+	if (rc)
+		goto out_irq;
 
 	return 0;
 
-out_work:
-	hrtimer_cancel(&ap_poll_timer);
+out_irq:
+	ap_irq_exit();
+out_device:
 	root_device_unregister(ap_root_device);
 out_bus:
 	bus_unregister(&ap_bus_type);
 out:
-	if (ap_irq_flag)
-		unregister_adapter_interrupt(&ap_airq);
-	kfree(ap_qci_info);
+	ap_debug_exit();
 	return rc;
 }
-device_initcall(ap_module_init);
+
+static void __exit ap_module_exit(void)
+{
+	ap_async_exit();
+	ap_irq_exit();
+	root_device_unregister(ap_root_device);
+	bus_unregister(&ap_bus_type);
+	ap_debug_exit();
+}
+
+module_init(ap_module_init);
+module_exit(ap_module_exit);