arm_pmu: arm64: Use NMIs for PMU

Add required PMU interrupt operations for NMIs. Request interrupt lines as
NMIs when possible, otherwise fall back to normal interrupts.

NMIs are only supported on the arm64 architecture with a GICv3 irqchip.

[Alexandru E.: Added that NMIs only work on arm64 + GICv3, print message
	when PMU is using NMIs]

Signed-off-by: Julien Thierry <julien.thierry@arm.com>
Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
Tested-by: Sumit Garg <sumit.garg@linaro.org> (Developerbox)
Cc: Julien Thierry <julien.thierry.kdev@gmail.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20200924110706.254996-8-alexandru.elisei@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

Author: Julien Thierry

drivers/perf/arm_pmu.c

@@ -45,6 +45,17 @@ static const struct pmu_irq_ops pmuirq_ops = {
 	.free_pmuirq = armpmu_free_pmuirq
 };
 
+static void armpmu_free_pmunmi(unsigned int irq, int cpu, void __percpu *devid)
+{
+	free_nmi(irq, per_cpu_ptr(devid, cpu));
+}
+
+static const struct pmu_irq_ops pmunmi_ops = {
+	.enable_pmuirq = enable_nmi,
+	.disable_pmuirq = disable_nmi_nosync,
+	.free_pmuirq = armpmu_free_pmunmi
+};
+
 static void armpmu_enable_percpu_pmuirq(unsigned int irq)
 {
 	enable_percpu_irq(irq, IRQ_TYPE_NONE);
@@ -63,10 +74,37 @@ static const struct pmu_irq_ops percpu_pmuirq_ops = {
 	.free_pmuirq = armpmu_free_percpu_pmuirq
 };
 
+static void armpmu_enable_percpu_pmunmi(unsigned int irq)
+{
+	if (!prepare_percpu_nmi(irq))
+		enable_percpu_nmi(irq, IRQ_TYPE_NONE);
+}
+
+static void armpmu_disable_percpu_pmunmi(unsigned int irq)
+{
+	disable_percpu_nmi(irq);
+	teardown_percpu_nmi(irq);
+}
+
+static void armpmu_free_percpu_pmunmi(unsigned int irq, int cpu,
+				      void __percpu *devid)
+{
+	if (armpmu_count_irq_users(irq) == 1)
+		free_percpu_nmi(irq, devid);
+}
+
+static const struct pmu_irq_ops percpu_pmunmi_ops = {
+	.enable_pmuirq = armpmu_enable_percpu_pmunmi,
+	.disable_pmuirq = armpmu_disable_percpu_pmunmi,
+	.free_pmuirq = armpmu_free_percpu_pmunmi
+};
+
 static DEFINE_PER_CPU(struct arm_pmu *, cpu_armpmu);
 static DEFINE_PER_CPU(int, cpu_irq);
 static DEFINE_PER_CPU(const struct pmu_irq_ops *, cpu_irq_ops);
 
+static bool has_nmi;
+
 static inline u64 arm_pmu_event_max_period(struct perf_event *event)
 {
 	if (event->hw.flags & ARMPMU_EVT_64BIT)
@@ -637,15 +675,31 @@ int armpmu_request_irq(int irq, int cpu)
 			    IRQF_NO_THREAD;
 
 		irq_set_status_flags(irq, IRQ_NOAUTOEN);
-		err = request_irq(irq, handler, irq_flags, "arm-pmu",
+
+		err = request_nmi(irq, handler, irq_flags, "arm-pmu",
 				  per_cpu_ptr(&cpu_armpmu, cpu));
 
-		irq_ops = &pmuirq_ops;
+		/* If cannot get an NMI, get a normal interrupt */
+		if (err) {
+			err = request_irq(irq, handler, irq_flags, "arm-pmu",
+					  per_cpu_ptr(&cpu_armpmu, cpu));
+			irq_ops = &pmuirq_ops;
+		} else {
+			has_nmi = true;
+			irq_ops = &pmunmi_ops;
+		}
 	} else if (armpmu_count_irq_users(irq) == 0) {
-		err = request_percpu_irq(irq, handler, "arm-pmu",
-					 &cpu_armpmu);
-
-		irq_ops = &percpu_pmuirq_ops;
+		err = request_percpu_nmi(irq, handler, "arm-pmu", &cpu_armpmu);
+
+		/* If cannot get an NMI, get a normal interrupt */
+		if (err) {
+			err = request_percpu_irq(irq, handler, "arm-pmu",
+						 &cpu_armpmu);
+			irq_ops = &percpu_pmuirq_ops;
+		} else {
+			has_nmi= true;
+			irq_ops = &percpu_pmunmi_ops;
+		}
 	} else {
 		/* Per cpudevid irq was already requested by another CPU */
 		irq_ops = armpmu_find_irq_ops(irq);
@@ -928,8 +982,9 @@ int armpmu_register(struct arm_pmu *pmu)
 	if (!__oprofile_cpu_pmu)
 		__oprofile_cpu_pmu = pmu;
 
-	pr_info("enabled with %s PMU driver, %d counters available\n",
-		pmu->name, pmu->num_events);
+	pr_info("enabled with %s PMU driver, %d counters available%s\n",
+		pmu->name, pmu->num_events,
+		has_nmi ? ", using NMIs" : "");
 
 	return 0;