[PATCH V12] powerpc/vphn: Update CPU topology when VPHN enabled

[Michael Bringmann <mwb@linux.vnet.ibm.com>]

powerpc/numa: On Power systems with shared configurations of CPUs
and memory, there are some issues with the association of additional
CPUs and memory to nodes when hot-adding resources.  This patch
addresses some of those problems.

First, it corrects the currently broken capability to set the
topology for shared CPUs in LPARs.  At boot time for shared CPU
lpars, the topology for each CPU was being set to node zero.  Now
when numa_update_cpu_topology() is called appropriately, the Virtual
Processor Home Node (VPHN) capabilities information provided by the
pHyp allows the appropriate node in the shared configuration to be
selected for the CPU.

Next, it updates the initialization checks to independently recognize
PRRN or VPHN support.

Next, during hotplug CPU operations, it resets the timer on topology
update work function to a small value to better ensure that the CPU
topology is detected and configured sooner.

Also, fix an end-of-updates processing problem observed occasionally
in numa_update_cpu_topology().

Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com>
---
Changes in V12:
  -- Reorganize some of the updates to minimize kernel impact.
  -- Improve documentation of this patch.
---
 arch/powerpc/include/asm/topology.h          |    8 +++
 arch/powerpc/mm/numa.c                       |   65 ++++++++++++++++++++++++--
 arch/powerpc/platforms/pseries/hotplug-cpu.c |    2 +
 3 files changed, 69 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/topology.h b/arch/powerpc/include/asm/topology.h
index dc4e159..600e1c6 100644
--- a/arch/powerpc/include/asm/topology.h
+++ b/arch/powerpc/include/asm/topology.h
@@ -98,6 +98,14 @@ static inline int prrn_is_enabled(void)
 }
 #endif /* CONFIG_NUMA && CONFIG_PPC_SPLPAR */
 
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_NEED_MULTIPLE_NODES)
+#if defined(CONFIG_PPC_SPLPAR)
+extern int timed_topology_update(int nsecs);
+#else
+#define	timed_topology_update(nsecs)	0
+#endif /* CONFIG_PPC_SPLPAR */
+#endif /* CONFIG_HOTPLUG_CPU || CONFIG_NEED_MULTIPLE_NODES */
+
 #include <asm-generic/topology.h>
 
 #ifdef CONFIG_SMP
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index b95c584..c8b965f 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -1148,11 +1148,32 @@ struct topology_update_data {
 	int new_nid;
 };
 
+#define	TOPOLOGY_DEF_TIMER_SECS		60
+
 static u8 vphn_cpu_change_counts[NR_CPUS][MAX_DISTANCE_REF_POINTS];
 static cpumask_t cpu_associativity_changes_mask;
 static int vphn_enabled;
 static int prrn_enabled;
 static void reset_topology_timer(void);
+static int topology_timer_secs = 1;
+static int topology_inited;
+static int topology_update_needed;
+
+/*
+ * Change polling interval for associativity changes.
+ */
+int timed_topology_update(int nsecs)
+{
+	if (nsecs > 0)
+		topology_timer_secs = nsecs;
+	else
+		topology_timer_secs = TOPOLOGY_DEF_TIMER_SECS;
+
+	if (vphn_enabled)
+		reset_topology_timer();
+
+	return 0;
+}
 
 /*
  * Store the current values of the associativity change counters in the
@@ -1246,6 +1267,11 @@ static long vphn_get_associativity(unsigned long cpu,
 			"hcall_vphn() experienced a hardware fault "
 			"preventing VPHN. Disabling polling...\n");
 		stop_topology_update();
+		break;
+	case H_SUCCESS:
+		dbg("VPHN hcall succeeded. Reset polling...\n");
+		timed_topology_update(0);
+		break;
 	}
 
 	return rc;
@@ -1323,8 +1349,11 @@ int numa_update_cpu_topology(bool cpus_locked)
 	struct device *dev;
 	int weight, new_nid, i = 0;
 
-	if (!prrn_enabled && !vphn_enabled)
+	if (!prrn_enabled && !vphn_enabled) {
+		if (!topology_inited)
+			topology_update_needed = 1;
 		return 0;
+	}
 
 	weight = cpumask_weight(&cpu_associativity_changes_mask);
 	if (!weight)
@@ -1363,6 +1392,8 @@ int numa_update_cpu_topology(bool cpus_locked)
 			cpumask_andnot(&cpu_associativity_changes_mask,
 					&cpu_associativity_changes_mask,
 					cpu_sibling_mask(cpu));
+			pr_info("Assoc chg gives same node %d for cpu%d\n",
+					new_nid, cpu);
 			cpu = cpu_last_thread_sibling(cpu);
 			continue;
 		}
@@ -1379,6 +1410,13 @@ int numa_update_cpu_topology(bool cpus_locked)
 		cpu = cpu_last_thread_sibling(cpu);
 	}
 
+	/*
+	 * Prevent processing of 'updates' from overflowing array
+	 * in cases where last entry filled in a 'next' pointer.
+	 */
+	if (i)
+		updates[i-1].next = NULL;
+
 	pr_debug("Topology update for the following CPUs:\n");
 	if (cpumask_weight(&updated_cpus)) {
 		for (ud = &updates[0]; ud; ud = ud->next) {
@@ -1433,6 +1471,7 @@ int numa_update_cpu_topology(bool cpus_locked)
 
 out:
 	kfree(updates);
+	topology_update_needed = 0;
 	return changed;
 }
 
@@ -1453,6 +1492,13 @@ static void topology_schedule_update(void)
 	schedule_work(&topology_work);
 }
 
+void shared_topology_update(void)
+{
+	if (firmware_has_feature(FW_FEATURE_VPHN) &&
+		   lppaca_shared_proc(get_lppaca()))
+		topology_schedule_update();
+}
+
 static void topology_timer_fn(unsigned long ignored)
 {
 	if (prrn_enabled && cpumask_weight(&cpu_associativity_changes_mask))
@@ -1469,7 +1515,7 @@ static void topology_timer_fn(unsigned long ignored)
 static void reset_topology_timer(void)
 {
 	topology_timer.data = 0;
-	topology_timer.expires = jiffies + 60 * HZ;
+	topology_timer.expires = jiffies + topology_timer_secs * HZ;
 	mod_timer(&topology_timer, topology_timer.expires);
 }
 
@@ -1519,15 +1565,14 @@ int start_topology_update(void)
 	if (firmware_has_feature(FW_FEATURE_PRRN)) {
 		if (!prrn_enabled) {
 			prrn_enabled = 1;
-			vphn_enabled = 0;
 #ifdef CONFIG_SMP
 			rc = of_reconfig_notifier_register(&dt_update_nb);
 #endif
 		}
-	} else if (firmware_has_feature(FW_FEATURE_VPHN) &&
+	}
+	if (firmware_has_feature(FW_FEATURE_VPHN) &&
 		   lppaca_shared_proc(get_lppaca())) {
 		if (!vphn_enabled) {
-			prrn_enabled = 0;
 			vphn_enabled = 1;
 			setup_cpu_associativity_change_counters();
 			init_timer_deferrable(&topology_timer);
@@ -1550,7 +1595,8 @@ int stop_topology_update(void)
 #ifdef CONFIG_SMP
 		rc = of_reconfig_notifier_unregister(&dt_update_nb);
 #endif
-	} else if (vphn_enabled) {
+	}
+	if (vphn_enabled) {
 		vphn_enabled = 0;
 		rc = del_timer_sync(&topology_timer);
 	}
@@ -1613,9 +1659,16 @@ static int topology_update_init(void)
 	if (topology_updates_enabled)
 		start_topology_update();
 
+	shared_topology_update();
+
 	if (!proc_create("powerpc/topology_updates", 0644, NULL, &topology_ops))
 		return -ENOMEM;
 
+	topology_inited = 1;
+	if (topology_update_needed)
+		bitmap_fill(cpumask_bits(&cpu_associativity_changes_mask),
+					nr_cpumask_bits);
+
 	return 0;
 }
 device_initcall(topology_update_init);
diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index 6afd1ef..5a7fb1e 100644
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -356,6 +356,7 @@ static int dlpar_online_cpu(struct device_node *dn)
 			BUG_ON(get_cpu_current_state(cpu)
 					!= CPU_STATE_OFFLINE);
 			cpu_maps_update_done();
+			timed_topology_update(1);
 			rc = device_online(get_cpu_device(cpu));
 			if (rc)
 				goto out;
@@ -522,6 +523,7 @@ static int dlpar_offline_cpu(struct device_node *dn)
 				set_preferred_offline_state(cpu,
 							    CPU_STATE_OFFLINE);
 				cpu_maps_update_done();
+				timed_topology_update(1);
 				rc = device_offline(get_cpu_device(cpu));
 				if (rc)
 					goto out;