From 48538b5863d8e8f8d567fc9a1d27a68623e0a0ff Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Fri, 9 Sep 2016 14:08:30 +0100 Subject: 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 00e727bb389359c8 ("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: Mark Rutland Cc: Will Deacon Signed-off-by: Will Deacon --- drivers/perf/arm_pmu.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'drivers/perf/arm_pmu.c') diff --git a/drivers/perf/arm_pmu.c b/drivers/perf/arm_pmu.c index 60c065eb638d..c36913ad3a09 100644 --- a/drivers/perf/arm_pmu.c +++ b/drivers/perf/arm_pmu.c @@ -534,6 +534,24 @@ static int armpmu_filter_match(struct perf_event *event) 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) { atomic_set(&armpmu->active_events, 0); @@ -551,6 +569,8 @@ static void armpmu_init(struct arm_pmu *armpmu) .filter_match = armpmu_filter_match, .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. */ -- cgit