[V13,-,RESEND,05/10] arm64/perf: Add branch stack support in ARMV8 PMU
Commit Message
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/arm/include/asm/arm_pmuv3.h | 9 +++
arch/arm64/include/asm/perf_event.h | 31 +++++++++++
drivers/perf/arm_pmuv3.c | 86 +++++++++++++++++++++--------
3 files changed, 102 insertions(+), 24 deletions(-)
@@ -249,4 +249,13 @@ static inline bool is_pmuv3p5(int pmuver)
return pmuver >= ARMV8_PMU_DFR_VER_V3P5;
}
+/* BRBE stubs */
+#ifdef CONFIG_PERF_EVENTS
+static inline void armv8pmu_branch_read(struct pmu_hw_events *cpuc, struct perf_event *event) { }
+static inline bool armv8pmu_branch_attr_valid(struct perf_event *event) { return false; }
+static inline void armv8pmu_branch_enable(struct perf_event *event) { }
+static inline void armv8pmu_branch_disable(struct perf_event *event) { }
+static inline void armv8pmu_branch_probe(struct arm_pmu *arm_pmu) { }
+static inline void armv8pmu_branch_reset(void) { }
+#endif
#endif
@@ -24,4 +24,35 @@ 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_attr_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) { }
+#endif
#endif
@@ -721,38 +721,21 @@ 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);
}
@@ -830,6 +813,11 @@ 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
@@ -928,6 +916,14 @@ 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 && armpmu->has_branch_stack)
+ armv8pmu_branch_reset();
+}
+
/*
* Add an event filter to a given event.
*/
@@ -998,6 +994,9 @@ static void armv8pmu_reset(void *info)
pmcr |= ARMV8_PMU_PMCR_LP;
armv8pmu_pmcr_write(pmcr);
+
+ if (cpu_pmu->has_branch_stack)
+ armv8pmu_branch_reset();
}
static int __armv8_pmuv3_map_event_id(struct arm_pmu *armpmu,
@@ -1035,6 +1034,9 @@ 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_attr_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
@@ -1151,6 +1153,33 @@ 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 branch_records __percpu *records;
+ int cpu;
+
+ records = alloc_percpu_gfp(struct branch_records, GFP_KERNEL);
+ if (!records)
+ return -ENOMEM;
+
+ /*
+ * FIXME: Memory allocated via records gets completely
+ * consumed here, never required to be freed up later. Hence
+ * losing access to on stack 'records' is acceptable.
+ * Otherwise this alloc handle has to be saved some where.
+ */
+ for_each_possible_cpu(cpu) {
+ struct pmu_hw_events *events_cpu;
+ struct branch_records *records_cpu;
+
+ events_cpu = per_cpu_ptr(armpmu->hw_events, cpu);
+ records_cpu = per_cpu_ptr(records, cpu);
+ events_cpu->branches = records_cpu;
+ }
+ return 0;
}
static int armv8pmu_probe_pmu(struct arm_pmu *cpu_pmu)
@@ -1167,7 +1196,15 @@ static int armv8pmu_probe_pmu(struct arm_pmu *cpu_pmu)
if (ret)
return ret;
- return probe.present ? 0 : -ENODEV;
+ if (!probe.present)
+ return -ENODEV;
+
+ if (cpu_pmu->has_branch_stack) {
+ ret = branch_records_alloc(cpu_pmu);
+ if (ret)
+ return ret;
+ }
+ return 0;
}
static void armv8pmu_disable_user_access_ipi(void *unused)
@@ -1230,6 +1267,7 @@ 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;