linux-kernel - [PATCH V2 2/2] perf tools: always set no branch for dummy event in PT

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Message-Id: <20170630141656.1626-2-kan.liang@intel.com>
Date:   Fri, 30 Jun 2017 10:16:56 -0400
From:   kan.liang@...el.com
To:     acme@...nel.org, jolsa@...hat.com, linux-kernel@...r.kernel.org
Cc:     mingo@...hat.com, peterz@...radead.org, adrian.hunter@...el.com,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com,
        Kan Liang <kan.liang@...el.com>
Subject: [PATCH V2 2/2] perf tools: always set no branch for dummy event in PT

From: Kan Liang <kan.liang@...el.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@...el.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