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Subject[PATCH V2 2/2] perf tools: always set no branch for dummy event in PT
Date
From: Kan Liang <kan.liang@intel.com>

An earlier kernel patch allowed enabling PT and LBR at the same time on
Goldmont.

commit ccbebba4c6bf ("perf/x86/intel/pt: Bypass PT vs. LBR exclusivity
if the core supports it")

However, users still cannot use Intel PT and LBRs simultaneously.
$ sudo perf record -e cycles,intel_pt//u -b -- sleep 1
Error:
PMU Hardware doesn't support sampling/overflow-interrupts.

PT implicitly adds dummy event in perf tool. dummy event is software
event which doesn't support LBR.

Always setting no branch for dummy event in Intel PT.

Signed-off-by: Kan Liang <kan.liang@intel.com>
---

Changes since V1
- change the BRANCH_STACK sample bit directly (jirka)

tools/perf/arch/x86/util/intel-pt.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
index 4fe1aed..2201f3b 100644
--- a/tools/perf/arch/x86/util/intel-pt.c
+++ b/tools/perf/arch/x86/util/intel-pt.c
@@ -700,6 +700,7 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
perf_evsel__set_sample_bit(switch_evsel, TID);
perf_evsel__set_sample_bit(switch_evsel, TIME);
perf_evsel__set_sample_bit(switch_evsel, CPU);
+ perf_evsel__reset_sample_bit(switch_evsel, BRANCH_STACK);

opts->record_switch_events = false;
ptr->have_sched_switch = 3;
@@ -761,6 +762,7 @@ static int intel_pt_recording_options(struct auxtrace_record *itr,
/* And the CPU for switch events */
perf_evsel__set_sample_bit(tracking_evsel, CPU);
}
+ perf_evsel__reset_sample_bit(tracking_evsel, BRANCH_STACK);
}

/*
--
2.9.4
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