[PATCH 16/75] perf intel-pt: Fix error with config term "pt=0"

Arnaldo Carvalho de Melo
2018-12-06T21:27:43Z

From: Adrian Hunter <adrian.hunter@intel.com>

Users should never use 'pt=0', but if they do it may give a meaningless
error:

$ perf record -e intel_pt/pt=0/u uname
Error:
The sys_perf_event_open() syscall returned with 22 (Invalid argument) for
event (intel_pt/pt=0/u).

Fix that by forcing 'pt=1'.

Committer testing:

# perf record -e intel_pt/pt=0/u uname
Error:
The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (intel_pt/pt=0/u).
/bin/dmesg | grep -i perf may provide additional information.

# perf record -e intel_pt/pt=0/u uname
pt=0 doesn't make sense, forcing pt=1
Linux
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.020 MB perf.data ]
#

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/b7c5b4e5-9497-10e5-fd43-5f3e4a0fe51d@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/arch/x86/util/intel-pt.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
index db0ba8caf5a2..ba8ecaf52200 100644
--- a/tools/perf/arch/x86/util/intel-pt.c
+++ b/tools/perf/arch/x86/util/intel-pt.c
@@ -524,10 +524,21 @@ static int intel_pt_validate_config(struct perf_pmu *intel_pt_pmu,
struct perf_evsel *evsel)
{
int err;
+ char c;

if (!evsel)
return 0;

+ /*
+ * If supported, force pass-through config term (pt=1) even if user
+ * sets pt=0, which avoids senseless kernel errors.
+ */
+ if (perf_pmu__scan_file(intel_pt_pmu, "format/pt", "%c", &c) == 1 &&
+ !(evsel->attr.config & 1)) {
+ pr_warning("pt=0 doesn't make sense, forcing pt=1\n");
+ evsel->attr.config |= 1;
+ }
+
err = intel_pt_val_config_term(intel_pt_pmu, "caps/cycle_thresholds",
"cyc_thresh", "caps/psb_cyc",
evsel->attr.config);
--
2.19.2