drivers/perf: xgene: Add CPU hotplug support

If the CPU assigned to the xgene PMU is taken offline, then subsequent
perf invocations on the PMU will fail:

  # echo 0 > /sys/devices/system/cpu/cpu0/online
  # perf stat -a -e l3c0/cycle-count/,l3c0/write/ sleep 1
    Error:
    The sys_perf_event_open() syscall returned with 19 (No such device) for event (l3c0/cycle-count/).
    /bin/dmesg may provide additional information.
    No CONFIG_PERF_EVENTS=y kernel support configured?

This patch implements a hotplug notifier in the xgene PMU driver so that
the PMU context is migrated to another online CPU should its assigned
CPU disappear.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Hoan Tran <hoan.tran@amperecomputing.com>
[will: Made naming of new cpuhp_state enum entry consistent]
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/drivers/perf/xgene_pmu.c b/drivers/perf/xgene_pmu.c
index 0e31f13..0dc9ff0 100644 (file)
--- a/drivers/perf/xgene_pmu.c
+++ b/drivers/perf/xgene_pmu.c
@@ -21,6 +21,7 @@
 
 #include <linux/acpi.h>
 #include <linux/clk.h>
+#include <linux/cpuhotplug.h>
 #include <linux/cpumask.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
@@ -130,12 +131,14 @@ struct xgene_pmu_ops {
 
 struct xgene_pmu {
        struct device *dev;
+       struct hlist_node node;
        int version;
        void __iomem *pcppmu_csr;
        u32 mcb_active_mask;
        u32 mc_active_mask;
        u32 l3c_active_mask;
        cpumask_t cpu;
+       int irq;
        raw_spinlock_t lock;
        const struct xgene_pmu_ops *ops;
        struct list_head l3cpmus;
@@ -1806,6 +1809,53 @@ static const struct acpi_device_id xgene_pmu_acpi_match[] = {
 MODULE_DEVICE_TABLE(acpi, xgene_pmu_acpi_match);
 #endif
 
+static int xgene_pmu_online_cpu(unsigned int cpu, struct hlist_node *node)
+{
+       struct xgene_pmu *xgene_pmu = hlist_entry_safe(node, struct xgene_pmu,
+                                                      node);
+
+       if (cpumask_empty(&xgene_pmu->cpu))
+               cpumask_set_cpu(cpu, &xgene_pmu->cpu);
+
+       /* Overflow interrupt also should use the same CPU */
+       WARN_ON(irq_set_affinity(xgene_pmu->irq, &xgene_pmu->cpu));
+
+       return 0;
+}
+
+static int xgene_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
+{
+       struct xgene_pmu *xgene_pmu = hlist_entry_safe(node, struct xgene_pmu,
+                                                      node);
+       struct xgene_pmu_dev_ctx *ctx;
+       unsigned int target;
+
+       if (!cpumask_test_and_clear_cpu(cpu, &xgene_pmu->cpu))
+               return 0;
+       target = cpumask_any_but(cpu_online_mask, cpu);
+       if (target >= nr_cpu_ids)
+               return 0;
+
+       list_for_each_entry(ctx, &xgene_pmu->mcpmus, next) {
+               perf_pmu_migrate_context(&ctx->pmu_dev->pmu, cpu, target);
+       }
+       list_for_each_entry(ctx, &xgene_pmu->mcbpmus, next) {
+               perf_pmu_migrate_context(&ctx->pmu_dev->pmu, cpu, target);
+       }
+       list_for_each_entry(ctx, &xgene_pmu->l3cpmus, next) {
+               perf_pmu_migrate_context(&ctx->pmu_dev->pmu, cpu, target);
+       }
+       list_for_each_entry(ctx, &xgene_pmu->iobpmus, next) {
+               perf_pmu_migrate_context(&ctx->pmu_dev->pmu, cpu, target);
+       }
+
+       cpumask_set_cpu(target, &xgene_pmu->cpu);
+       /* Overflow interrupt also should use the same CPU */
+       WARN_ON(irq_set_affinity(xgene_pmu->irq, &xgene_pmu->cpu));
+
+       return 0;
+}
+
 static int xgene_pmu_probe(struct platform_device *pdev)
 {
        const struct xgene_pmu_data *dev_data;
@@ -1815,6 +1865,14 @@ static int xgene_pmu_probe(struct platform_device *pdev)
        int irq, rc;
        int version;
 
+       /* Install a hook to update the reader CPU in case it goes offline */
+       rc = cpuhp_setup_state_multi(CPUHP_AP_PERF_ARM_APM_XGENE_ONLINE,
+                                     "CPUHP_AP_PERF_ARM_APM_XGENE_ONLINE",
+                                     xgene_pmu_online_cpu,
+                                     xgene_pmu_offline_cpu);
+       if (rc)
+               return rc;
+
        xgene_pmu = devm_kzalloc(&pdev->dev, sizeof(*xgene_pmu), GFP_KERNEL);
        if (!xgene_pmu)
                return -ENOMEM;
@@ -1865,6 +1923,7 @@ static int xgene_pmu_probe(struct platform_device *pdev)
                dev_err(&pdev->dev, "No IRQ resource\n");
                return -EINVAL;
        }
+
        rc = devm_request_irq(&pdev->dev, irq, xgene_pmu_isr,
                                IRQF_NOBALANCING | IRQF_NO_THREAD,
                                dev_name(&pdev->dev), xgene_pmu);
@@ -1873,6 +1932,8 @@ static int xgene_pmu_probe(struct platform_device *pdev)
                return rc;
        }
 
+       xgene_pmu->irq = irq;
+
        raw_spin_lock_init(&xgene_pmu->lock);
 
        /* Check for active MCBs and MCUs */
@@ -1883,13 +1944,11 @@ static int xgene_pmu_probe(struct platform_device *pdev)
                xgene_pmu->mc_active_mask = 0x1;
        }
 
-       /* Pick one core to use for cpumask attributes */
-       cpumask_set_cpu(smp_processor_id(), &xgene_pmu->cpu);
-
-       /* Make sure that the overflow interrupt is handled by this CPU */
-       rc = irq_set_affinity(irq, &xgene_pmu->cpu);
+       /* Add this instance to the list used by the hotplug callback */
+       rc = cpuhp_state_add_instance(CPUHP_AP_PERF_ARM_APM_XGENE_ONLINE,
+                                     &xgene_pmu->node);
        if (rc) {
-               dev_err(&pdev->dev, "Failed to set interrupt affinity!\n");
+               dev_err(&pdev->dev, "Error %d registering hotplug", rc);
                return rc;
        }
 
@@ -1897,13 +1956,18 @@ static int xgene_pmu_probe(struct platform_device *pdev)
        rc = xgene_pmu_probe_pmu_dev(xgene_pmu, pdev);
        if (rc) {
                dev_err(&pdev->dev, "No PMU perf devices found!\n");
-               return rc;
+               goto out_unregister;
        }
 
        /* Enable interrupt */
        xgene_pmu->ops->unmask_int(xgene_pmu);
 
        return 0;
+
+out_unregister:
+       cpuhp_state_remove_instance(CPUHP_AP_PERF_ARM_APM_XGENE_ONLINE,
+                                   &xgene_pmu->node);
+       return rc;
 }
 
 static void
@@ -1924,6 +1988,8 @@ static int xgene_pmu_remove(struct platform_device *pdev)
        xgene_pmu_dev_cleanup(xgene_pmu, &xgene_pmu->iobpmus);
        xgene_pmu_dev_cleanup(xgene_pmu, &xgene_pmu->mcbpmus);
        xgene_pmu_dev_cleanup(xgene_pmu, &xgene_pmu->mcpmus);
+       cpuhp_state_remove_instance(CPUHP_AP_PERF_ARM_APM_XGENE_ONLINE,
+                                   &xgene_pmu->node);
 
        return 0;
 }

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index e0cd2ba..d007a31 100644 (file)
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -164,6 +164,7 @@ enum cpuhp_state {
        CPUHP_AP_PERF_ARM_L2X0_ONLINE,
        CPUHP_AP_PERF_ARM_QCOM_L2_ONLINE,
        CPUHP_AP_PERF_ARM_QCOM_L3_ONLINE,
+       CPUHP_AP_PERF_ARM_APM_XGENE_ONLINE,
        CPUHP_AP_PERF_POWERPC_NEST_IMC_ONLINE,
        CPUHP_AP_PERF_POWERPC_CORE_IMC_ONLINE,
        CPUHP_AP_PERF_POWERPC_THREAD_IMC_ONLINE,