linux-kernel - [PATCH V2 03/12] perf intel-pt: Support Z itrace option for timeless decoding

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Date:   Fri, 30 Apr 2021 10:03:00 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH V2 03/12] perf intel-pt: Support Z itrace option for timeless decoding

Correlating virtual machine TSC packets is not supported at present, so
instead support the Z itrace option.

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
---
 tools/perf/Documentation/perf-intel-pt.txt | 5 +++++
 tools/perf/util/intel-pt.c                 | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Documentation/perf-intel-pt.txt b/tools/perf/Documentation/perf-intel-pt.txt
index 1dcec73c910c..33df7898c378 100644
--- a/tools/perf/Documentation/perf-intel-pt.txt
+++ b/tools/perf/Documentation/perf-intel-pt.txt
@@ -869,6 +869,7 @@ The letters are:
 	L	synthesize last branch entries on existing event records
 	s	skip initial number of events
 	q	quicker (less detailed) decoding
+	Z	prefer to ignore timestamps (so-called "timeless" decoding)
 
 "Instructions" events look like they were recorded by "perf record -e
 instructions".
@@ -1062,6 +1063,10 @@ What *will* be decoded with the qq option:
 
 	- instruction pointer associated with PSB packets
 
+The Z option is equivalent to having recorded a trace without TSC
+(i.e. config term tsc=0). It can be useful to avoid timestamp issues when
+decoding a trace of a virtual machine.
+
 
 dump option
 ~~~~~~~~~~~
diff --git a/tools/perf/util/intel-pt.c b/tools/perf/util/intel-pt.c
index eef8970d98fe..7bee969eb335 100644
--- a/tools/perf/util/intel-pt.c
+++ b/tools/perf/util/intel-pt.c
@@ -899,7 +899,7 @@ static bool intel_pt_timeless_decoding(struct intel_pt *pt)
 	bool timeless_decoding = true;
 	u64 config;
 
-	if (!pt->tsc_bit || !pt->cap_user_time_zero)
+	if (!pt->tsc_bit || !pt->cap_user_time_zero || pt->synth_opts.timeless_decoding)
 		return true;
 
 	evlist__for_each_entry(pt->session->evlist, evsel) {
-- 
2.25.1