Commit cbb72a3c authored by Hoan Tran's avatar Hoan Tran Committed by Will Deacon
Browse files

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: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarHoan Tran <hoan.tran@amperecomputing.com>
[will: Made naming of new cpuhp_state enum entry consistent]
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 472dc9fa

drivers/perf/xgene_pmu.c

+73 −7
Original line number Diff line number Diff line
@@ -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;

}

include/linux/cpuhotplug.h

+1 −0
Original line number Diff line number Diff line
@@ -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,

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