Commit 46284c6c authored by Kan Liang's avatar Kan Liang Committed by Joerg Roedel
Browse files

iommu/vt-d: Support cpumask for IOMMU perfmon 



The perf subsystem assumes that all counters are by default per-CPU. So
the user space tool reads a counter from each CPU. However, the IOMMU
counters are system-wide and can be read from any CPU. Here we use a CPU
mask to restrict counting to one CPU to handle the issue. (with CPU
hotplug notifier to choose a different CPU if the chosen one is taken
off-line).

The CPU is exposed to /sys/bus/event_source/devices/dmar*/cpumask for
the user space perf tool.

Signed-off-by: default avatarKan Liang <kan.liang@linux.intel.com>
Link: https://lore.kernel.org/r/20230128200428.1459118-6-kan.liang@linux.intel.com


Signed-off-by: default avatarLu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent 7232ab8b

Documentation/ABI/testing/sysfs-bus-event_source-devices-iommu

+8 −0
Original line number Diff line number Diff line
@@ -27,3 +27,11 @@ Description: Read-only. Attribute group to describe the magic bits 
		    filter_pasid	= "config2:0-21"  - PASID filter

		    filter_ats		= "config2:24-28" - Address Type filter

		    filter_page_table	= "config2:32-36" - Page Table Level filter



What:		/sys/bus/event_source/devices/dmar*/cpumask

Date:		Jan 2023

KernelVersion:	6.3

Contact:	Kan Liang <kan.liang@linux.intel.com>

Description:	Read-only. This file always returns the CPU to which the

		IOMMU pmu is bound for access to all IOMMU pmu performance

		monitoring events.

drivers/iommu/intel/perfmon.c

+105 −8
Original line number Diff line number Diff line
@@ -34,9 +34,28 @@ static struct attribute_group iommu_pmu_events_attr_group = { 
	.attrs = attrs_empty,

};



static cpumask_t iommu_pmu_cpu_mask;



static ssize_t

cpumask_show(struct device *dev, struct device_attribute *attr, char *buf)

{

	return cpumap_print_to_pagebuf(true, buf, &iommu_pmu_cpu_mask);

}

static DEVICE_ATTR_RO(cpumask);



static struct attribute *iommu_pmu_cpumask_attrs[] = {

	&dev_attr_cpumask.attr,

	NULL

};



static struct attribute_group iommu_pmu_cpumask_attr_group = {

	.attrs = iommu_pmu_cpumask_attrs,

};



static const struct attribute_group *iommu_pmu_attr_groups[] = {

	&iommu_pmu_format_attr_group,

	&iommu_pmu_events_attr_group,

	&iommu_pmu_cpumask_attr_group,

	NULL

};
@@ -679,20 +698,98 @@ void free_iommu_pmu(struct intel_iommu *iommu) 
	iommu->pmu = NULL;

}



void iommu_pmu_register(struct intel_iommu *iommu)

static int iommu_pmu_cpu_online(unsigned int cpu)

{

	if (cpumask_empty(&iommu_pmu_cpu_mask))

		cpumask_set_cpu(cpu, &iommu_pmu_cpu_mask);



	return 0;

}



static int iommu_pmu_cpu_offline(unsigned int cpu)

{

	struct dmar_drhd_unit *drhd;

	struct intel_iommu *iommu;

	int target;



	if (!cpumask_test_and_clear_cpu(cpu, &iommu_pmu_cpu_mask))

		return 0;



	target = cpumask_any_but(cpu_online_mask, cpu);



	if (target < nr_cpu_ids)

		cpumask_set_cpu(target, &iommu_pmu_cpu_mask);

	else

		target = -1;



	rcu_read_lock();



	for_each_iommu(iommu, drhd) {

		if (!iommu->pmu)

			continue;

		perf_pmu_migrate_context(&iommu->pmu->pmu, cpu, target);

	}

	rcu_read_unlock();



	return 0;

}



static int nr_iommu_pmu;



static int iommu_pmu_cpuhp_setup(struct iommu_pmu *iommu_pmu)

{

	int ret;



	if (nr_iommu_pmu++)

		return 0;



	ret = cpuhp_setup_state(CPUHP_AP_PERF_X86_IOMMU_PERF_ONLINE,

				"driver/iommu/intel/perfmon:online",

				iommu_pmu_cpu_online,

				iommu_pmu_cpu_offline);

	if (ret)

		nr_iommu_pmu = 0;



	return ret;

}



static void iommu_pmu_cpuhp_free(struct iommu_pmu *iommu_pmu)

{

	if (--nr_iommu_pmu)

		return;



	if (__iommu_pmu_register(iommu)) {

		pr_err("Failed to register PMU for iommu (seq_id = %d)\n",

		       iommu->seq_id);

		free_iommu_pmu(iommu);

	cpuhp_remove_state(CPUHP_AP_PERF_X86_IOMMU_PERF_ONLINE);

}



void iommu_pmu_register(struct intel_iommu *iommu)

{

	struct iommu_pmu *iommu_pmu = iommu->pmu;



	if (!iommu_pmu)

		return;



	if (__iommu_pmu_register(iommu))

		goto err;



	if (iommu_pmu_cpuhp_setup(iommu_pmu))

		goto unregister;



	return;



unregister:

	perf_pmu_unregister(&iommu_pmu->pmu);

err:

	pr_err("Failed to register PMU for iommu (seq_id = %d)\n", iommu->seq_id);

	free_iommu_pmu(iommu);

}



void iommu_pmu_unregister(struct intel_iommu *iommu)

{

	if (iommu->pmu)

		perf_pmu_unregister(&iommu->pmu->pmu);

	struct iommu_pmu *iommu_pmu = iommu->pmu;



	if (!iommu_pmu)

		return;



	iommu_pmu_cpuhp_free(iommu_pmu);

	perf_pmu_unregister(&iommu_pmu->pmu);

}

include/linux/cpuhotplug.h

+1 −0
Original line number Diff line number Diff line
@@ -221,6 +221,7 @@ enum cpuhp_state { 
	CPUHP_AP_PERF_X86_CQM_ONLINE,

	CPUHP_AP_PERF_X86_CSTATE_ONLINE,

	CPUHP_AP_PERF_X86_IDXD_ONLINE,

	CPUHP_AP_PERF_X86_IOMMU_PERF_ONLINE,

	CPUHP_AP_PERF_S390_CF_ONLINE,

	CPUHP_AP_PERF_S390_SF_ONLINE,

	CPUHP_AP_PERF_ARM_CCI_ONLINE,