[PATCH v1 3/9]powerpc/powernv: Add cpu hotplug support

[Madhavan Srinivasan]

Patch adds cpu hotplug support. First online cpu in a node is picked as
designated thread to read the Nest pmu counter data, and at the time of
hotplug, next online cpu from the same node is picked up.

Cc: Michael Ellerman <mpe at ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Paul Mackerras <paulus at samba.org>
Cc: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
Cc: Anshuman Khandual <khandual at linux.vnet.ibm.com>
Cc: Stephane Eranian <eranian at google.com>
Cc: Preeti U Murthy <preeti at linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo at kernel.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Signed-off-by: Madhavan Srinivasan <maddy at linux.vnet.ibm.com>
---
 arch/powerpc/perf/nest-pmu.c | 84 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)

diff --git a/arch/powerpc/perf/nest-pmu.c b/arch/powerpc/perf/nest-pmu.c
index d4413bb..3e7010e 100644
--- a/arch/powerpc/perf/nest-pmu.c
+++ b/arch/powerpc/perf/nest-pmu.c
@@ -30,6 +30,86 @@ static struct attribute_group cpumask_nest_pmu_attr_group = {
 	.attrs = cpumask_nest_pmu_attrs,
 };
 
+static void nest_init(void *dummy)
+{
+	opal_nest_ima_control(P8_NEST_ENGINE_START);
+}
+
+static void nest_change_cpu_context(int old_cpu, int new_cpu)
+{
+	int i;
+
+	for (i=0; per_nestpmu_arr[i] != NULL; i++)
+		perf_pmu_migrate_context(&per_nestpmu_arr[i]->pmu,
+						old_cpu, new_cpu);
+	return;
+}
+
+static void nest_exit_cpu(int cpu)
+{
+	int i, nid, target = -1;
+	const struct cpumask *l_cpumask;
+	int src_chipid;
+
+	if (!cpumask_test_and_clear_cpu(cpu, &cpu_mask_nest_pmu))
+		return;
+
+	nid = cpu_to_node(cpu);
+	src_chipid = topology_physical_package_id(cpu);
+	l_cpumask = cpumask_of_node(nid);
+	for_each_cpu(i, l_cpumask) {
+		if (i == cpu)
+			continue;
+		if (src_chipid == topology_physical_package_id(i)) {
+			target = i;
+			break;
+		}
+	}
+
+	cpumask_set_cpu(target, &cpu_mask_nest_pmu);
+	nest_change_cpu_context (cpu, target);
+	return;
+}
+
+static void nest_init_cpu(int cpu)
+{
+	int i, src_chipid;
+
+	src_chipid = topology_physical_package_id(cpu);
+	for_each_cpu(i, &cpu_mask_nest_pmu)
+		if (src_chipid == topology_physical_package_id(i))
+			return;
+
+	cpumask_set_cpu(cpu, &cpu_mask_nest_pmu);
+	nest_change_cpu_context ( -1, cpu);
+	return;
+}
+
+static int nest_cpu_notifier(struct notifier_block *self,
+				unsigned long action, void *hcpu)
+{
+	unsigned int cpu = (long)hcpu;
+
+	switch (action & ~CPU_TASKS_FROZEN) {
+	case CPU_DOWN_FAILED:
+	case CPU_STARTING:
+		nest_init_cpu(cpu);
+		break;
+	case CPU_DOWN_PREPARE:
+		nest_exit_cpu(cpu);
+		break;
+	default:
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block nest_cpu_nb = {
+	.notifier_call  = nest_cpu_notifier,
+	.priority       = CPU_PRI_PERF + 1,
+}
+
 void cpumask_chip(void)
 {
 	const struct cpumask *l_cpumask;
@@ -47,6 +127,10 @@ void cpumask_chip(void)
 		cpumask_set_cpu(cpu, &cpu_mask_nest_pmu);
 	}
 
+	on_each_cpu_mask(&cpu_mask_nest_pmu, (smp_call_func_t)nest_init, NULL, 1);
+
+	__register_cpu_notifier(&nest_cpu_nb);
+
 	cpu_notifier_register_done();
 }
 
-- 
1.9.1