Messages in this thread | | | Date | Thu, 9 Jun 2022 10:32:40 +0530 | Subject | Re: [PATCH V5] arm64: perf: Make exporting of pmu events configurable | From | Srinivasarao Pathipati <> |
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Hi Will / Robin ,
Could you please review this change.
On 5/23/2022 5:19 PM, Srinivasarao Pathipati wrote: > The PMU export bit (PMCR_EL0.X) is getting reset during pmu reset, > Make is configurable using sysctls to enable/disable at runtime. > It can also be enabled at early bootup with kernel arguments. > > Signed-off-by: Srinivasarao Pathipati <quic_c_spathi@quicinc.com> > --- > Changes since V4: > - Registering sysctls dynamically for only arm64 as suggested by Will > - Not removed the code to configure with kernel parameters > as the sysctl's kernel parameter(sysctl.kernel.export_pmu_events) > is not working at early bootup. pmu_reset() getting called before > sysctl's kernel parameter is set. > Changes since V3: > - export bit is now configurable with sysctl > - enabling export bit on reset instead of retaining > > Changes since V2: > Done below changes as per Will's comments > - enabling pmcr_x now configurable with kernel parameters and > by default it is disabled. > > Changes since V1: > - Preserving only PMCR_X bit as per Robin Murphy's comment. > > --- > Documentation/admin-guide/kernel-parameters.txt | 5 +++++ > Documentation/admin-guide/sysctl/kernel.rst | 9 +++++++++ > arch/arm64/kernel/perf_event.c | 24 ++++++++++++++++++++++++ > 3 files changed, 38 insertions(+) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index de3da15..2bf1187 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -5150,6 +5150,11 @@ > Useful for devices that are detected asynchronously > (e.g. USB and MMC devices). > > + export_pmu_events > + [KNL,ARM64] Sets the PMU export bit (PMCR_EL0.X), which enables > + the exporting of events over an IMPLEMENTATION DEFINED PMU event > + export bus to another device. > + > retain_initrd [RAM] Keep initrd memory after extraction > > rfkill.default_state= > diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst > index ddccd10..db42d4c 100644 > --- a/Documentation/admin-guide/sysctl/kernel.rst > +++ b/Documentation/admin-guide/sysctl/kernel.rst > @@ -892,6 +892,15 @@ The default value is 0 (access disabled). > > See Documentation/arm64/perf.rst for more information. > > +export_pmu_events (arm64 only) > +============================== > +Controls the PMU export bit (PMCR_EL0.X), which enables the exporting of > +events over an IMPLEMENTATION DEFINED PMU event export bus to another device. > + > +0: disables exporting of events (default). > + > +1: enables exporting of events. > + > > pid_max > ======= > diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c > index cb69ff1..d93e7c4 100644 > --- a/arch/arm64/kernel/perf_event.c > +++ b/arch/arm64/kernel/perf_event.c > @@ -298,6 +298,7 @@ PMU_FORMAT_ATTR(long, "config1:0"); > PMU_FORMAT_ATTR(rdpmc, "config1:1"); > > static int sysctl_perf_user_access __read_mostly; > +static int sysctl_export_pmu_events __read_mostly; > > static inline bool armv8pmu_event_is_64bit(struct perf_event *event) > { > @@ -1025,6 +1026,17 @@ static int armv8pmu_filter_match(struct perf_event *event) > return evtype != ARMV8_PMUV3_PERFCTR_CHAIN; > } > > +static int __init export_pmu_events(char *str) > +{ > + /* Enable exporting of pmu events at early bootup with kernel > + * arguments. > + */ > + sysctl_export_pmu_events = 1; > + return 0; > +} > + > +early_param("export_pmu_events", export_pmu_events); > + > static void armv8pmu_reset(void *info) > { > struct arm_pmu *cpu_pmu = (struct arm_pmu *)info; > @@ -1047,6 +1059,9 @@ static void armv8pmu_reset(void *info) > if (armv8pmu_has_long_event(cpu_pmu)) > pmcr |= ARMV8_PMU_PMCR_LP; > > + if (sysctl_export_pmu_events) > + pmcr |= ARMV8_PMU_PMCR_X; > + > armv8pmu_pmcr_write(pmcr); > } > > @@ -1221,6 +1236,15 @@ static struct ctl_table armv8_pmu_sysctl_table[] = { > .extra1 = SYSCTL_ZERO, > .extra2 = SYSCTL_ONE, > }, > + { > + .procname = "export_pmu_events", > + .data = &sysctl_export_pmu_events, > + .maxlen = sizeof(unsigned int), > + .mode = 0644, > + .proc_handler = proc_dointvec_minmax, > + .extra1 = SYSCTL_ZERO, > + .extra2 = SYSCTL_ONE, > + }, > { } > }; >
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