[PATCH v3 18/26] perf: arm_pmu: Request specific affinities for percpu NMI/IRQ

Marc Zyngier
2025-09-22T08:28:49Z

From: Will Deacon <will@kernel.org>

Let the PMU driver request both NMI and normal IRQs with an affinity
mask matching the PMU affinity.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
drivers/perf/arm_pmu.c | 44 +++++++++++++++++++--------------
drivers/perf/arm_pmu_acpi.c | 2 +-
drivers/perf/arm_pmu_platform.c | 4 +--
include/linux/perf/arm_pmu.h | 4 +--
4 files changed, 31 insertions(+), 23 deletions(-)

diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c
index 22c601b46c858..959ceb3d1f556 100644
--- a/drivers/perf/arm_pmu.c
+++ b/drivers/perf/arm_pmu.c
@@ -26,7 +26,8 @@

#include <asm/irq_regs.h>

-static int armpmu_count_irq_users(const int irq);
+static int armpmu_count_irq_users(const struct cpumask *affinity,
+ const int irq);

struct pmu_irq_ops {
void (*enable_pmuirq)(unsigned int irq);
@@ -64,7 +65,9 @@ static void armpmu_enable_percpu_pmuirq(unsigned int irq)
static void armpmu_free_percpu_pmuirq(unsigned int irq, int cpu,
void __percpu *devid)
{
- if (armpmu_count_irq_users(irq) == 1)
+ struct arm_pmu *armpmu = *per_cpu_ptr((void * __percpu *)devid, cpu);
+
+ if (armpmu_count_irq_users(&armpmu->supported_cpus, irq) == 1)
free_percpu_irq(irq, devid);
}

@@ -89,7 +92,9 @@ static void armpmu_disable_percpu_pmunmi(unsigned int irq)
static void armpmu_free_percpu_pmunmi(unsigned int irq, int cpu,
void __percpu *devid)
{
- if (armpmu_count_irq_users(irq) == 1)
+ struct arm_pmu *armpmu = *per_cpu_ptr((void * __percpu *)devid, cpu);
+
+ if (armpmu_count_irq_users(&armpmu->supported_cpus, irq) == 1)
free_percpu_nmi(irq, devid);
}

@@ -580,11 +585,11 @@ static const struct attribute_group armpmu_common_attr_group = {
.attrs = armpmu_common_attrs,
};

-static int armpmu_count_irq_users(const int irq)
+static int armpmu_count_irq_users(const struct cpumask *affinity, const int irq)
{
int cpu, count = 0;

- for_each_possible_cpu(cpu) {
+ for_each_cpu(cpu, affinity) {
if (per_cpu(cpu_irq, cpu) == irq)
count++;
}
@@ -592,12 +597,13 @@ static int armpmu_count_irq_users(const int irq)
return count;
}

-static const struct pmu_irq_ops *armpmu_find_irq_ops(int irq)
+static const struct pmu_irq_ops *
+armpmu_find_irq_ops(const struct cpumask *affinity, int irq)
{
const struct pmu_irq_ops *ops = NULL;
int cpu;

- for_each_possible_cpu(cpu) {
+ for_each_cpu(cpu, affinity) {
if (per_cpu(cpu_irq, cpu) != irq)
continue;

@@ -609,22 +615,25 @@ static const struct pmu_irq_ops *armpmu_find_irq_ops(int irq)
return ops;
}

-void armpmu_free_irq(int irq, int cpu)
+void armpmu_free_irq(struct arm_pmu * __percpu *armpmu, int irq, int cpu)
{
if (per_cpu(cpu_irq, cpu) == 0)
return;
if (WARN_ON(irq != per_cpu(cpu_irq, cpu)))
return;

- per_cpu(cpu_irq_ops, cpu)->free_pmuirq(irq, cpu, &cpu_armpmu);
+ per_cpu(cpu_irq_ops, cpu)->free_pmuirq(irq, cpu, armpmu);

per_cpu(cpu_irq, cpu) = 0;
per_cpu(cpu_irq_ops, cpu) = NULL;
}

-int armpmu_request_irq(int irq, int cpu)
+int armpmu_request_irq(struct arm_pmu * __percpu *pcpu_armpmu, int irq, int cpu)
{
int err = 0;
+ struct arm_pmu **armpmu = per_cpu_ptr(pcpu_armpmu, cpu);
+ const struct cpumask *affinity = *armpmu ? &(*armpmu)->supported_cpus :
+ cpu_possible_mask; /* ACPI */
const irq_handler_t handler = armpmu_dispatch_irq;
const struct pmu_irq_ops *irq_ops;

@@ -646,25 +655,24 @@ int armpmu_request_irq(int irq, int cpu)
IRQF_NOBALANCING | IRQF_NO_AUTOEN |
IRQF_NO_THREAD;

- err = request_nmi(irq, handler, irq_flags, "arm-pmu",
- per_cpu_ptr(&cpu_armpmu, cpu));
+ err = request_nmi(irq, handler, irq_flags, "arm-pmu", armpmu);

/* 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));
+ armpmu);
irq_ops = &pmuirq_ops;
} else {
has_nmi = true;
irq_ops = &pmunmi_ops;
}
- } else if (armpmu_count_irq_users(irq) == 0) {
- err = request_percpu_nmi(irq, handler, "arm-pmu", NULL, &cpu_armpmu);
+ } else if (armpmu_count_irq_users(affinity, irq) == 0) {
+ err = request_percpu_nmi(irq, handler, "arm-pmu", affinity, pcpu_armpmu);

/* If cannot get an NMI, get a normal interrupt */
if (err) {
- err = request_percpu_irq(irq, handler, "arm-pmu",
- &cpu_armpmu);
+ err = request_percpu_irq_affinity(irq, handler, "arm-pmu",
+ affinity, pcpu_armpmu);
irq_ops = &percpu_pmuirq_ops;
} else {
has_nmi = true;
@@ -672,7 +680,7 @@ int armpmu_request_irq(int irq, int cpu)
}
} else {
/* Per cpudevid irq was already requested by another CPU */
- irq_ops = armpmu_find_irq_ops(irq);
+ irq_ops = armpmu_find_irq_ops(affinity, irq);

if (WARN_ON(!irq_ops))
err = -EINVAL;
diff --git a/drivers/perf/arm_pmu_acpi.c b/drivers/perf/arm_pmu_acpi.c
index 05dda19c5359a..e80f76d95e68b 100644
--- a/drivers/perf/arm_pmu_acpi.c
+++ b/drivers/perf/arm_pmu_acpi.c
@@ -218,7 +218,7 @@ static int arm_pmu_acpi_parse_irqs(void)
* them with their PMUs.
*/
per_cpu(pmu_irqs, cpu) = irq;
- err = armpmu_request_irq(irq, cpu);
+ err = armpmu_request_irq(&probed_pmus, irq, cpu);
if (err)
goto out_err;
}
diff --git a/drivers/perf/arm_pmu_platform.c b/drivers/perf/arm_pmu_platform.c
index 9c0494d8a867a..1c9e50a132015 100644
--- a/drivers/perf/arm_pmu_platform.c
+++ b/drivers/perf/arm_pmu_platform.c
@@ -165,7 +165,7 @@ static int armpmu_request_irqs(struct arm_pmu *armpmu)
if (!irq)
continue;

- err = armpmu_request_irq(irq, cpu);
+ err = armpmu_request_irq(&hw_events->percpu_pmu, irq, cpu);
if (err)
break;
}
@@ -181,7 +181,7 @@ static void armpmu_free_irqs(struct arm_pmu *armpmu)
for_each_cpu(cpu, &armpmu->supported_cpus) {
int irq = per_cpu(hw_events->irq, cpu);

- armpmu_free_irq(irq, cpu);
+ armpmu_free_irq(&hw_events->percpu_pmu, irq, cpu);
}
}

diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
index 93c9a26492fcf..6690bd77aa4ee 100644
--- a/include/linux/perf/arm_pmu.h
+++ b/include/linux/perf/arm_pmu.h
@@ -190,8 +190,8 @@ bool arm_pmu_irq_is_nmi(void);
struct arm_pmu *armpmu_alloc(void);
void armpmu_free(struct arm_pmu *pmu);
int armpmu_register(struct arm_pmu *pmu);
-int armpmu_request_irq(int irq, int cpu);
-void armpmu_free_irq(int irq, int cpu);
+int armpmu_request_irq(struct arm_pmu * __percpu *armpmu, int irq, int cpu);
+void armpmu_free_irq(struct arm_pmu * __percpu *armpmu, int irq, int cpu);

#define ARMV8_PMU_PDEV_NAME "armv8-pmu"

--
2.47.3