Messages in this thread Patch in this message | | | From | Srinivasarao Pathipati <> | Subject | [PATCH V4] arm64: perf: Set PMCR.X of PMCR_EL0 during pmu reset | Date | Mon, 16 May 2022 18:25:38 +0530 |
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Enable exporting of events over PMU event export bus by setting PMCR.X of PMCR_EL0 during pmu reset.
As it impacts power consumption make it configurable at bootup with kernel arguments and at runtime with sysctl.
Signed-off-by: Srinivasarao Pathipati <quic_c_spathi@quicinc.com> --- 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 | 4 ++++ Documentation/admin-guide/sysctl/kernel.rst | 8 ++++++++ arch/arm64/kernel/perf_event.c | 15 +++++++++++++++ include/linux/perf_event.h | 1 + kernel/sysctl.c | 12 ++++++++++++ 5 files changed, 40 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index de3da15..2139b81 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5150,6 +5150,10 @@ Useful for devices that are detected asynchronously (e.g. USB and MMC devices). + export_pmu_events + [KNL] Sets export bit of PMCR_EL0 to enable the exporting of + events over PMU event export bus. + 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..8fbc3a0 100644 --- a/Documentation/admin-guide/sysctl/kernel.rst +++ b/Documentation/admin-guide/sysctl/kernel.rst @@ -892,6 +892,14 @@ The default value is 0 (access disabled). See Documentation/arm64/perf.rst for more information. +export_pmu_events +================= +Controls the export bit(4th bit) of PMCR_EL0 which enables the exporting of +events over an IMPLEMENTATION DEFINED PMU event export bus to another device. + +0: disables exporting of events + +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..271a8c6 100644 --- a/arch/arm64/kernel/perf_event.c +++ b/arch/arm64/kernel/perf_event.c @@ -34,6 +34,7 @@ #define ARMV8_THUNDER_PERFCTR_L1I_CACHE_PREF_ACCESS 0xEC #define ARMV8_THUNDER_PERFCTR_L1I_CACHE_PREF_MISS 0xED +int sysctl_export_pmu_events __read_mostly; /* * ARMv8 Architectural defined events, not all of these may * be supported on any given implementation. Unsupported events will @@ -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) +{ + /* Exporting of events can be enabled at runtime with sysctl or + * statically at bootup with kernel parameters. + */ + 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); } diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index da75956..7790328 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1311,6 +1311,7 @@ extern void put_callchain_entry(int rctx); extern int sysctl_perf_event_max_stack; extern int sysctl_perf_event_max_contexts_per_stack; +extern int sysctl_export_pmu_events; static inline int perf_callchain_store_context(struct perf_callchain_entry_ctx *ctx, u64 ip) { diff --git a/kernel/sysctl.c b/kernel/sysctl.c index e52b6e3..3b751a2e 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -2008,6 +2008,18 @@ static struct ctl_table kern_table[] = { .extra2 = SYSCTL_ONE_THOUSAND, }, #endif +#ifdef CONFIG_HW_PERF_EVENTS + { + .procname = "export_pmu_events", + .data = &sysctl_export_pmu_events, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + + }, +#endif { .procname = "panic_on_warn", .data = &panic_on_warn, -- 2.7.4
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