Messages in this thread | | | From | Namhyung Kim <> | Date | Thu, 1 Jun 2023 19:33:54 -0700 | Subject | Re: [PATCH V11 05/10] arm64/perf: Add branch stack support in ARMV8 PMU |
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On Tue, May 30, 2023 at 9:27 PM Anshuman Khandual <anshuman.khandual@arm.com> wrote: > > This enables support for branch stack sampling event in ARMV8 PMU, checking > has_branch_stack() on the event inside 'struct arm_pmu' callbacks. Although > these branch stack helpers armv8pmu_branch_XXXXX() are just dummy functions > for now. While here, this also defines arm_pmu's sched_task() callback with > armv8pmu_sched_task(), which resets the branch record buffer on a sched_in. > > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Tested-by: James Clark <james.clark@arm.com> > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > arch/arm64/include/asm/perf_event.h | 33 +++++++++++++ > drivers/perf/arm_pmuv3.c | 76 ++++++++++++++++++++--------- > 2 files changed, 86 insertions(+), 23 deletions(-) > > diff --git a/arch/arm64/include/asm/perf_event.h b/arch/arm64/include/asm/perf_event.h > index eb7071c9eb34..7548813783ba 100644 > --- a/arch/arm64/include/asm/perf_event.h > +++ b/arch/arm64/include/asm/perf_event.h > @@ -24,4 +24,37 @@ extern unsigned long perf_misc_flags(struct pt_regs *regs); > (regs)->pstate = PSR_MODE_EL1h; \ > } > > +struct pmu_hw_events; > +struct arm_pmu; > +struct perf_event; > + > +#ifdef CONFIG_PERF_EVENTS > +static inline bool has_branch_stack(struct perf_event *event); > + > +static inline void armv8pmu_branch_read(struct pmu_hw_events *cpuc, struct perf_event *event) > +{ > + WARN_ON_ONCE(!has_branch_stack(event)); > +} > + > +static inline bool armv8pmu_branch_valid(struct perf_event *event) > +{ > + WARN_ON_ONCE(!has_branch_stack(event)); > + return false; > +} > + > +static inline void armv8pmu_branch_enable(struct perf_event *event) > +{ > + WARN_ON_ONCE(!has_branch_stack(event)); > +} > + > +static inline void armv8pmu_branch_disable(struct perf_event *event) > +{ > + WARN_ON_ONCE(!has_branch_stack(event)); > +} > + > +static inline void armv8pmu_branch_probe(struct arm_pmu *arm_pmu) { } > +static inline void armv8pmu_branch_reset(void) { } > +static inline int armv8pmu_private_alloc(struct arm_pmu *arm_pmu) { return 0; } > +static inline void armv8pmu_private_free(struct arm_pmu *arm_pmu) { } > +#endif > #endif > diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c > index c98e4039386d..86d803ff1ae3 100644 > --- a/drivers/perf/arm_pmuv3.c > +++ b/drivers/perf/arm_pmuv3.c > @@ -705,38 +705,21 @@ static void armv8pmu_enable_event(struct perf_event *event) > * Enable counter and interrupt, and set the counter to count > * the event that we're interested in. > */ > - > - /* > - * Disable counter > - */ > armv8pmu_disable_event_counter(event); > - > - /* > - * Set event. > - */ > armv8pmu_write_event_type(event); > - > - /* > - * Enable interrupt for this counter > - */ > armv8pmu_enable_event_irq(event); > - > - /* > - * Enable counter > - */ > armv8pmu_enable_event_counter(event); > + > + if (has_branch_stack(event)) > + armv8pmu_branch_enable(event); > } > > static void armv8pmu_disable_event(struct perf_event *event) > { > - /* > - * Disable counter > - */ > - armv8pmu_disable_event_counter(event); > + if (has_branch_stack(event)) > + armv8pmu_branch_disable(event); > > - /* > - * Disable interrupt for this counter > - */ > + armv8pmu_disable_event_counter(event); > armv8pmu_disable_event_irq(event); > } > > @@ -814,6 +797,11 @@ static irqreturn_t armv8pmu_handle_irq(struct arm_pmu *cpu_pmu) > if (!armpmu_event_set_period(event)) > continue; > > + if (has_branch_stack(event) && !WARN_ON(!cpuc->branches)) { > + armv8pmu_branch_read(cpuc, event); > + perf_sample_save_brstack(&data, event, &cpuc->branches->branch_stack); > + } > + > /* > * Perf event overflow will queue the processing of the event as > * an irq_work which will be taken care of in the handling of > @@ -912,6 +900,14 @@ static int armv8pmu_user_event_idx(struct perf_event *event) > return event->hw.idx; > } > > +static void armv8pmu_sched_task(struct perf_event_pmu_context *pmu_ctx, bool sched_in) > +{ > + struct arm_pmu *armpmu = to_arm_pmu(pmu_ctx->pmu); > + > + if (sched_in && arm_pmu_branch_stack_supported(armpmu)) > + armv8pmu_branch_reset(); > +} > + > /* > * Add an event filter to a given event. > */ > @@ -982,6 +978,9 @@ static void armv8pmu_reset(void *info) > pmcr |= ARMV8_PMU_PMCR_LP; > > armv8pmu_pmcr_write(pmcr); > + > + if (arm_pmu_branch_stack_supported(cpu_pmu)) > + armv8pmu_branch_reset(); > } > > static int __armv8_pmuv3_map_event_id(struct arm_pmu *armpmu, > @@ -1019,6 +1018,9 @@ static int __armv8_pmuv3_map_event(struct perf_event *event, > > hw_event_id = __armv8_pmuv3_map_event_id(armpmu, event); > > + if (has_branch_stack(event) && !armv8pmu_branch_valid(event)) > + return -EOPNOTSUPP; > + > /* > * CHAIN events only work when paired with an adjacent counter, and it > * never makes sense for a user to open one in isolation, as they'll be > @@ -1135,6 +1137,21 @@ static void __armv8pmu_probe_pmu(void *info) > cpu_pmu->reg_pmmir = read_pmmir(); > else > cpu_pmu->reg_pmmir = 0; > + armv8pmu_branch_probe(cpu_pmu); > +} > + > +static int branch_records_alloc(struct arm_pmu *armpmu) > +{ > + struct pmu_hw_events *events; > + int cpu; > + > + for_each_possible_cpu(cpu) { > + events = per_cpu_ptr(armpmu->hw_events, cpu); > + events->branches = kzalloc(sizeof(struct branch_records), GFP_KERNEL); > + if (!events->branches) > + return -ENOMEM; > + } > + return 0; > } > > static int armv8pmu_probe_pmu(struct arm_pmu *cpu_pmu) > @@ -1145,12 +1162,24 @@ static int armv8pmu_probe_pmu(struct arm_pmu *cpu_pmu) > }; > int ret; > > + ret = armv8pmu_private_alloc(cpu_pmu); > + if (ret) > + return ret;
Wouldn't it be better to move it under the if statement below if it's only needed for branch stack?
> + > ret = smp_call_function_any(&cpu_pmu->supported_cpus, > __armv8pmu_probe_pmu, > &probe, 1); > if (ret) > return ret;
Otherwise you might need to free it here.
> > + if (arm_pmu_branch_stack_supported(cpu_pmu)) { > + ret = branch_records_alloc(cpu_pmu); > + if (ret) > + return ret;
And here too.
Thanks, Namhyung
> + } else { > + armv8pmu_private_free(cpu_pmu); > + } > + > return probe.present ? 0 : -ENODEV; > } > > @@ -1214,6 +1243,7 @@ static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name, > cpu_pmu->set_event_filter = armv8pmu_set_event_filter; > > cpu_pmu->pmu.event_idx = armv8pmu_user_event_idx; > + cpu_pmu->sched_task = armv8pmu_sched_task; > > cpu_pmu->name = name; > cpu_pmu->map_event = map_event; > -- > 2.25.1 >
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