linux-kernel - [PATCH V4 3/5] perf/x86/intel/ds: Introduce read function for auto-reload event

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Date:   Mon, 12 Feb 2018 14:20:33 -0800
From:   kan.liang@...ux.intel.com
To:     peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Cc:     acme@...nel.org, tglx@...utronix.de, jolsa@...hat.com,
        eranian@...gle.com, ak@...ux.intel.com,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: [PATCH V4 3/5] perf/x86/intel/ds: Introduce read function for auto-reload event

From: Kan Liang <kan.liang@...ux.intel.com>

There is no way to get exact auto-reload times and value which needed
for event update unless flush the PEBS buffer.

Introduce intel_pmu_auto_reload_read() to drain the PEBS buffer for
auto reload event.
To prevent the race, the drain_pebs() only be called when the PMU is
disabled.

Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
---
 arch/x86/events/intel/ds.c   | 9 +++++++++
 arch/x86/events/perf_event.h | 2 ++
 2 files changed, 11 insertions(+)

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index f519ebc..406f3ba 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1303,6 +1303,15 @@ get_next_pebs_record_by_bit(void *base, void *top, int bit)
 	return NULL;
 }
 
+void intel_pmu_auto_reload_read(struct perf_event *event)
+{
+	WARN_ON(!(event->hw.flags & PERF_X86_EVENT_AUTO_RELOAD));
+
+	perf_pmu_disable(event->pmu);
+	intel_pmu_drain_pebs_buffer();
+	perf_pmu_enable(event->pmu);
+}
+
 /*
  * Special variant of intel_pmu_save_and_restart() for auto-reload.
  */
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 805400b..f4720a9 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -923,6 +923,8 @@ void intel_pmu_pebs_disable_all(void);
 
 void intel_pmu_pebs_sched_task(struct perf_event_context *ctx, bool sched_in);
 
+void intel_pmu_auto_reload_read(struct perf_event *event);
+
 void intel_ds_init(void);
 
 void intel_pmu_lbr_sched_task(struct perf_event_context *ctx, bool sched_in);
-- 
2.7.4