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Message-Id: <20230315051444.1683170-6-anshuman.khandual@arm.com>
Date: Wed, 15 Mar 2023 10:44:39 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
will@...nel.org, catalin.marinas@....com, mark.rutland@....com
Cc: Anshuman Khandual <anshuman.khandual@....com>,
Mark Brown <broonie@...nel.org>,
James Clark <james.clark@....com>,
Rob Herring <robh@...nel.org>, Marc Zyngier <maz@...nel.org>,
Suzuki Poulose <suzuki.poulose@....com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
linux-perf-users@...r.kernel.org
Subject: [PATCH V9 05/10] arm64/perf: Add branch stack support in ARMV8 PMU
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@....com>
Cc: Will Deacon <will@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
arch/arm64/include/asm/perf_event.h | 33 +++++++++++++
arch/arm64/kernel/perf_event.c | 77 ++++++++++++++++++++---------
2 files changed, 87 insertions(+), 23 deletions(-)
diff --git a/arch/arm64/include/asm/perf_event.h b/arch/arm64/include/asm/perf_event.h
index 3eaf462f5752..463f23c3484f 100644
--- a/arch/arm64/include/asm/perf_event.h
+++ b/arch/arm64/include/asm/perf_event.h
@@ -273,4 +273,37 @@ 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/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index dde06c0f97f3..6d7c4f91cbf7 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -769,38 +769,21 @@ 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);
}
@@ -878,6 +861,12 @@ 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
@@ -976,6 +965,14 @@ 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.
*/
@@ -1046,6 +1043,9 @@ 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(struct perf_event *event,
@@ -1063,6 +1063,9 @@ static int __armv8_pmuv3_map_event(struct perf_event *event,
&armv8_pmuv3_perf_cache_map,
ARMV8_PMU_EVTYPE_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
@@ -1183,6 +1186,21 @@ static void __armv8pmu_probe_pmu(void *info)
cpu_pmu->reg_pmmir = read_cpuid(PMMIR_EL1);
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)
@@ -1193,12 +1211,24 @@ static int armv8pmu_probe_pmu(struct arm_pmu *cpu_pmu)
};
int ret;
+ ret = armv8pmu_private_alloc(cpu_pmu);
+ if (ret)
+ return ret;
+
ret = smp_call_function_any(&cpu_pmu->supported_cpus,
__armv8pmu_probe_pmu,
&probe, 1);
if (ret)
return ret;
+ if (arm_pmu_branch_stack_supported(cpu_pmu)) {
+ ret = branch_records_alloc(cpu_pmu);
+ if (ret)
+ return ret;
+ } else {
+ armv8pmu_private_free(cpu_pmu);
+ }
+
return probe.present ? 0 : -ENODEV;
}
@@ -1262,6 +1292,7 @@ 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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