ARM: perf: use cpumask_t to record active IRQs

Commit 5dfc54e0 ("ARM: GIC: avoid routing interrupts to offline CPUs")
prevents the GIC from setting the affinity of an IRQ to a CPU with
id >= nr_cpu_ids. This was previously abused by perf on some platforms
where more IRQs were registered than possible CPUs.

This patch fixes the problem by using a cpumask_t to keep track of the
active (requested) interrupts in perf. The same effect could be achieved
by limiting the number of IRQs to the number of CPUs, but using a mask
instead will be useful for adding extended CPU hotplug support in the
future.

Acked-by: Jamie Iles <jamie@jamieiles.com>
Reviewed-by: Jean Pihet <j-pihet@ti.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 31 insertions, 33 deletions

diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 8514855ffc2..d507fe148e0 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -69,6 +69,7 @@ static DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events);
 
 struct arm_pmu {
         enum arm_perf_pmu_ids id;
+        cpumask_t       active_irqs;
         const char      *name;
         irqreturn_t     (*handle_irq)(int irq_num, void *dev);
         void            (*enable)(struct hw_perf_event *evt, int idx);
@@ -388,6 +389,25 @@ static irqreturn_t armpmu_platform_irq(int irq, void *dev)
         return plat->handle_irq(irq, dev, armpmu->handle_irq);
 }
 
+static void
+armpmu_release_hardware(void)
+{
+        int i, irq, irqs;
+
+        irqs = min(pmu_device->num_resources, num_possible_cpus());
+
+        for (i = 0; i < irqs; ++i) {
+                if (!cpumask_test_and_clear_cpu(i, &armpmu->active_irqs))
+                        continue;
+                irq = platform_get_irq(pmu_device, i);
+                if (irq >= 0)
+                        free_irq(irq, NULL);
+        }
+
+        armpmu->stop();
+        release_pmu(ARM_PMU_DEVICE_CPU);
+}
+
 static int
 armpmu_reserve_hardware(void)
 {
@@ -401,20 +421,20 @@ armpmu_reserve_hardware(void)
                 return err;
         }
 
-        irqs = pmu_device->num_resources;
-
         plat = dev_get_platdata(&pmu_device->dev);
         if (plat && plat->handle_irq)
                 handle_irq = armpmu_platform_irq;
         else
                 handle_irq = armpmu->handle_irq;
 
+        irqs = min(pmu_device->num_resources, num_possible_cpus());
         if (irqs < 1) {
                 pr_err("no irqs for PMUs defined\n");
                 return -ENODEV;
         }
 
         for (i = 0; i < irqs; ++i) {
+                err = 0;
                 irq = platform_get_irq(pmu_device, i);
                 if (irq < 0)
                         continue;
@@ -422,13 +442,12 @@ armpmu_reserve_hardware(void)
                 /*
                  * If we have a single PMU interrupt that we can't shift,
                  * assume that we're running on a uniprocessor machine and
-                 * continue.
+                 * continue. Otherwise, continue without this interrupt.
                  */
-                err = irq_set_affinity(irq, cpumask_of(i));
-                if (err && irqs > 1) {
-                        pr_err("unable to set irq affinity (irq=%d, cpu=%u)\n",
-                                irq, i);
-                        break;
+                if (irq_set_affinity(irq, cpumask_of(i)) && irqs > 1) {
+                        pr_warning("unable to set irq affinity (irq=%d, cpu=%u)\n",
+                                    irq, i);
+                        continue;
                 }
 
                 err = request_irq(irq, handle_irq,
@@ -437,35 +456,14 @@ armpmu_reserve_hardware(void)
                 if (err) {
                         pr_err("unable to request IRQ%d for ARM PMU counters\n",
                                 irq);
-                        break;
+                        armpmu_release_hardware();
+                        return err;
                 }
-        }
 
-        if (err) {
-                for (i = i - 1; i >= 0; --i) {
-                        irq = platform_get_irq(pmu_device, i);
-                        if (irq >= 0)
-                                free_irq(irq, NULL);
-                }
-                release_pmu(ARM_PMU_DEVICE_CPU);
+                cpumask_set_cpu(i, &armpmu->active_irqs);
         }
 
-        return err;
-}
-
-static void
-armpmu_release_hardware(void)
-{
-        int i, irq;
-
-        for (i = pmu_device->num_resources - 1; i >= 0; --i) {
-                irq = platform_get_irq(pmu_device, i);
-                if (irq >= 0)
-                        free_irq(irq, NULL);
-        }
-        armpmu->stop();
-
-        release_pmu(ARM_PMU_DEVICE_CPU);
+        return 0;
 }
 
 static atomic_t active_events = ATOMIC_INIT(0);