Commit dcb5cdf6 authored by Kajol Jain's avatar Kajol Jain Committed by Michael Ellerman
Browse files

powerpc/perf/hv-gpci: Add cpu hotplug support 



Patch here adds cpu hotplug functions to hv_gpci pmu.
A new cpuhp_state "CPUHP_AP_PERF_POWERPC_HV_GPCI_ONLINE" enum
is added.

The online callback function updates the cpumask only if its
empty. As the primary intention of adding hotplug support
is to designate a CPU to make HCALL to collect the
counter data.

The offline function test and clear corresponding cpu in a cpumask
and update cpumask to any other active cpu.

Signed-off-by: default avatarKajol Jain <kjain@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201003074943.338618-4-kjain@linux.ibm.com
parent 435387dd

arch/powerpc/perf/hv-gpci.c

+46 −0
Original line number Diff line number Diff line
@@ -48,6 +48,8 @@ EVENT_DEFINE_RANGE_FORMAT(length, config1, 24, 31); 
/* u32, byte offset */

EVENT_DEFINE_RANGE_FORMAT(offset, config1, 32, 63);



static cpumask_t hv_gpci_cpumask;



static struct attribute *format_attrs[] = {

	&format_attr_request.attr,

	&format_attr_starting_index.attr,
@@ -266,6 +268,45 @@ static struct pmu h_gpci_pmu = { 
	.capabilities = PERF_PMU_CAP_NO_EXCLUDE,

};



static int ppc_hv_gpci_cpu_online(unsigned int cpu)

{

	if (cpumask_empty(&hv_gpci_cpumask))

		cpumask_set_cpu(cpu, &hv_gpci_cpumask);



	return 0;

}



static int ppc_hv_gpci_cpu_offline(unsigned int cpu)

{

	int target;



	/* Check if exiting cpu is used for collecting gpci events */

	if (!cpumask_test_and_clear_cpu(cpu, &hv_gpci_cpumask))

		return 0;



	/* Find a new cpu to collect gpci events */

	target = cpumask_last(cpu_active_mask);



	if (target < 0 || target >= nr_cpu_ids) {

		pr_err("hv_gpci: CPU hotplug init failed\n");

		return -1;

	}



	/* Migrate gpci events to the new target */

	cpumask_set_cpu(target, &hv_gpci_cpumask);

	perf_pmu_migrate_context(&h_gpci_pmu, cpu, target);



	return 0;

}



static int hv_gpci_cpu_hotplug_init(void)

{

	return cpuhp_setup_state(CPUHP_AP_PERF_POWERPC_HV_GPCI_ONLINE,

			  "perf/powerpc/hv_gcpi:online",

			  ppc_hv_gpci_cpu_online,

			  ppc_hv_gpci_cpu_offline);

}



static int hv_gpci_init(void)

{

	int r;
@@ -286,6 +327,11 @@ static int hv_gpci_init(void) 
		return -ENODEV;

	}



	/* init cpuhotplug */

	r = hv_gpci_cpu_hotplug_init();

	if (r)

		return r;



	/* sampling not supported */

	h_gpci_pmu.capabilities |= PERF_PMU_CAP_NO_INTERRUPT;

include/linux/cpuhotplug.h

+1 −0
Original line number Diff line number Diff line
@@ -183,6 +183,7 @@ enum cpuhp_state { 
	CPUHP_AP_PERF_POWERPC_THREAD_IMC_ONLINE,

	CPUHP_AP_PERF_POWERPC_TRACE_IMC_ONLINE,

	CPUHP_AP_PERF_POWERPC_HV_24x7_ONLINE,

	CPUHP_AP_PERF_POWERPC_HV_GPCI_ONLINE,

	CPUHP_AP_WATCHDOG_ONLINE,

	CPUHP_AP_WORKQUEUE_ONLINE,

	CPUHP_AP_RCUTREE_ONLINE,

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