Messages in this thread Patch in this message | | | From | Srinivasarao Pathipati <> | Subject | [PATCH V5] arm64: perf: Make exporting of pmu events configurable | Date | Mon, 23 May 2022 17:19:34 +0530 |
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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, + }, { } }; -- 2.7.4
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