Commit 48538b58 authored by Mark Rutland's avatar Mark Rutland Committed by Will Deacon

drivers/perf: arm_pmu: expose a cpumask in sysfs

In systems with heterogeneous CPUs, there are multiple logical CPU PMUs,
each of which covers a subset of CPUs in the system. In some cases
userspace needs to know which CPUs a given logical PMU covers, so we'd
like to expose a cpumask under sysfs, similar to what is done for uncore
PMUs.

Unfortunately, prior to commit 00e727bb ("perf stat: Balance
opening and reading events"), perf stat only correctly handled a cpumask
holding a single CPU, and only when profiling in system-wide mode. In
other cases, the presence of a cpumask file could cause perf stat to
behave erratically.

Thus, exposing a cpumask file would break older perf binaries in cases
where they would otherwise work.

To avoid this issue while still providing userspace with the information
it needs, this patch exposes a differently-named file (cpus) under
sysfs. New tools can look for this and operate correctly, while older
tools will not be adversely affected by its presence.
Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 1589680d
...@@ -534,6 +534,24 @@ static int armpmu_filter_match(struct perf_event *event) ...@@ -534,6 +534,24 @@ static int armpmu_filter_match(struct perf_event *event)
return cpumask_test_cpu(cpu, &armpmu->supported_cpus); return cpumask_test_cpu(cpu, &armpmu->supported_cpus);
} }
static ssize_t armpmu_cpumask_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct arm_pmu *armpmu = to_arm_pmu(dev_get_drvdata(dev));
return cpumap_print_to_pagebuf(true, buf, &armpmu->supported_cpus);
}
static DEVICE_ATTR(cpus, S_IRUGO, armpmu_cpumask_show, NULL);
static struct attribute *armpmu_common_attrs[] = {
&dev_attr_cpus.attr,
NULL,
};
static struct attribute_group armpmu_common_attr_group = {
.attrs = armpmu_common_attrs,
};
static void armpmu_init(struct arm_pmu *armpmu) static void armpmu_init(struct arm_pmu *armpmu)
{ {
atomic_set(&armpmu->active_events, 0); atomic_set(&armpmu->active_events, 0);
...@@ -551,6 +569,8 @@ static void armpmu_init(struct arm_pmu *armpmu) ...@@ -551,6 +569,8 @@ static void armpmu_init(struct arm_pmu *armpmu)
.filter_match = armpmu_filter_match, .filter_match = armpmu_filter_match,
.attr_groups = armpmu->attr_groups, .attr_groups = armpmu->attr_groups,
}; };
armpmu->attr_groups[ARMPMU_ATTR_GROUP_COMMON] =
&armpmu_common_attr_group;
} }
/* Set at runtime when we know what CPU type we are. */ /* Set at runtime when we know what CPU type we are. */
......
...@@ -78,6 +78,7 @@ struct pmu_hw_events { ...@@ -78,6 +78,7 @@ struct pmu_hw_events {
}; };
enum armpmu_attr_groups { enum armpmu_attr_groups {
ARMPMU_ATTR_GROUP_COMMON,
ARMPMU_ATTR_GROUP_EVENTS, ARMPMU_ATTR_GROUP_EVENTS,
ARMPMU_ATTR_GROUP_FORMATS, ARMPMU_ATTR_GROUP_FORMATS,
ARMPMU_NR_ATTR_GROUPS ARMPMU_NR_ATTR_GROUPS
......
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