perf intel-pt: Fix error with config term "pt=0"

[ Upstream commit 1c6f709b9f96366cc47af23c05ecec9b8c0c392d ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
index db0ba8c..ba8ecaf 100644 (file)
--- 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);