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Subject[PATCH 24/28] perf evsel: Provide meaningful warning when trying to use 'aux_output' on older kernels
Date
From: Arnaldo Carvalho de Melo <acme@redhat.com>

Just like we do with the 'write_backwards' feature:

Before:

# perf record -e {intel_pt/branch=0/,cycles/aux-output/ppp} uname
Error:
The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (cycles/aux-output/ppp).
/bin/dmesg | grep -i perf may provide additional information.

#

After:

# perf record -e {intel_pt/branch=0/,cycles/aux-output/ppp} uname
Error:
The 'aux_output' feature is not supported, update the kernel.
#

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/n/tip-wgjsjroe1e150c0metgwmqwd@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/evsel.c | 11 +++++++++--
tools/perf/util/evsel.h | 1 +
2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 5da40511546b..0a33f7322ecc 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1738,7 +1738,8 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map *cpus,
int pid = -1, err;
enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit = NO_CHANGE;

- if (perf_missing_features.write_backward && evsel->core.attr.write_backward)
+ if ((perf_missing_features.write_backward && evsel->core.attr.write_backward) ||
+ (perf_missing_features.aux_output && evsel->core.attr.aux_output))
return -EINVAL;

if (cpus == NULL) {
@@ -1912,7 +1913,11 @@ int evsel__open(struct evsel *evsel, struct perf_cpu_map *cpus,
* Must probe features in the order they were added to the
* perf_event_attr interface.
*/
- if (!perf_missing_features.bpf_event && evsel->core.attr.bpf_event) {
+ if (!perf_missing_features.aux_output && evsel->core.attr.aux_output) {
+ perf_missing_features.aux_output = true;
+ pr_debug2("Kernel has no attr.aux_output support, bailing out\n");
+ goto out_close;
+ } else if (!perf_missing_features.bpf_event && evsel->core.attr.bpf_event) {
perf_missing_features.bpf_event = true;
pr_debug2("switching off bpf_event\n");
goto fallback_missing_features;
@@ -2926,6 +2931,8 @@ int perf_evsel__open_strerror(struct evsel *evsel, struct target *target,
return scnprintf(msg, size, "clockid feature not supported.");
if (perf_missing_features.clockid_wrong)
return scnprintf(msg, size, "wrong clockid (%d).", clockid);
+ if (perf_missing_features.aux_output)
+ return scnprintf(msg, size, "The 'aux_output' feature is not supported, update the kernel.");
break;
default:
break;
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 8a316dd54cd0..9cd6e3ae479a 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -184,6 +184,7 @@ struct perf_missing_features {
bool group_read;
bool ksymbol;
bool bpf_event;
+ bool aux_output;
};

extern struct perf_missing_features perf_missing_features;
--
2.21.0
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