perf/x86/intel/ds: Introduce ->read() function for auto-reload events and flush the PEBS buffer there

There is no way to get exact auto-reload times and values which are needed
for event updates unless we flush the PEBS buffer.

Introduce intel_pmu_auto_reload_read() to drain the PEBS buffer for
auto reload event. To prevent races with the hardware, we can only
call drain_pebs() when the PMU is disabled.

Signed-off-by: Kan Liang <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vince Weaver <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

2 files changed, 11 insertions, 0 deletions

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index f39a4df3a7bd..73844025adaf 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1306,6 +1306,15 @@ 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 d445f0026989..91643472f385 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -924,6 +924,8 @@ 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);