From: Rob Herring <r...@kernel.org> commit e2012600810c9ded81f6f63a8d04781be3c300ad upstream
Like x86, some users may want to disable userspace PMU counter altogether. Add a sysctl 'perf_user_access' file to control userspace counter access. The default is '0' which is disabled. Writing '1' enables access. Note that x86 supports globally enabling user access by writing '2' to /sys/bus/event_source/devices/cpu/rdpmc. As there's not existing userspace support to worry about, this shouldn't be necessary for Arm. It could be added later if the need arises. Cc: Peter Zijlstra <pet...@infradead.org> Cc: Ingo Molnar <mi...@redhat.com> Cc: Arnaldo Carvalho de Melo <a...@kernel.org> Cc: Alexander Shishkin <alexander.shish...@linux.intel.com> Cc: Jiri Olsa <jo...@redhat.com> Cc: Namhyung Kim <namhy...@kernel.org> Cc: Catalin Marinas <catalin.mari...@arm.com> Cc: linux-perf-us...@vger.kernel.org Acked-by: Will Deacon <w...@kernel.org> Reviewed-by: Mark Rutland <mark.rutl...@arm.com> Signed-off-by: Rob Herring <r...@kernel.org> Link: https://lore.kernel.org/r/20211208201124.310740-4-r...@kernel.org Signed-off-by: Will Deacon <w...@kernel.org> Signed-off-by: Adrian Zaharia <adrian.zaha...@windriver.com> --- Documentation/admin-guide/sysctl/kernel.rst | 11 +++++++++++ arch/arm64/kernel/perf_event.c | 17 +++++++++++++++++ 2 files changed, 28 insertions(+) diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst index a4b1ebc2e70b..93a828288034 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -898,6 +898,17 @@ enabled, otherwise writing to this file will return ``-EBUSY``. The default value is 8. +perf_user_access (arm64 only) +================================= + +Controls user space access for reading perf event counters. When set to 1, +user space can read performance monitor counter registers directly. + +The default value is 0 (access disabled). + +See Documentation/arm64/perf.rst for more information. + + pid_max ======= diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c index cdb3d4549b3a..bba0b0e24de4 100644 --- a/arch/arm64/kernel/perf_event.c +++ b/arch/arm64/kernel/perf_event.c @@ -289,6 +289,8 @@ static struct attribute_group armv8_pmuv3_events_attr_group = { PMU_FORMAT_ATTR(event, "config:0-15"); PMU_FORMAT_ATTR(long, "config1:0"); +static int sysctl_perf_user_access __read_mostly; + static inline bool armv8pmu_event_is_64bit(struct perf_event *event) { return event->attr.config1 & 0x1; @@ -1075,6 +1077,19 @@ static int armv8pmu_probe_pmu(struct arm_pmu *cpu_pmu) return probe.present ? 0 : -ENODEV; } +static struct ctl_table armv8_pmu_sysctl_table[] = { + { + .procname = "perf_user_access", + .data = &sysctl_perf_user_access, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, + { } +}; + static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name, int (*map_event)(struct perf_event *event), const struct attribute_group *events, @@ -1107,6 +1122,8 @@ static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name, cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_CAPS] = caps ? caps : &armv8_pmuv3_caps_attr_group; + register_sysctl("kernel", armv8_pmu_sysctl_table); + return 0; } -- 2.36.1
-=-=-=-=-=-=-=-=-=-=-=- Links: You receive all messages sent to this group. View/Reply Online (#12037): https://lists.yoctoproject.org/g/linux-yocto/message/12037 Mute This Topic: https://lists.yoctoproject.org/mt/95765178/21656 Group Owner: linux-yocto+ow...@lists.yoctoproject.org Unsubscribe: https://lists.yoctoproject.org/g/linux-yocto/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
