Commit ab0809af authored Mar 22, 2022 by Kim Phillips Committed by Arnaldo Carvalho de Melo Mar 26, 2022

perf evsel: Improve AMD IBS (Instruction-Based Sampling) error handling messages



Improve the error message returned on failed perf_event_open() on AMD
systems when using IBS (Instruction-Based Sampling).

Output of executing 'perf record -e ibs_op// true' as a non root user
BEFORE this patch (perf will add the 'u' modifier at the end to exclude
kernel/hypervisor sampling):

  The sys_perf_event_open() syscall returned with 22 (Invalid argument)for event (ibs_op//u).
  /bin/dmesg | grep -i perf may provide additional information.

Output after:

  AMD IBS can't exclude kernel events.  Try running at a higher privilege level.

Output of executing 'sudo perf record -e ibs_op// true' BEFORE this patch:

  Error:
  The sys_perf_event_open() syscall returned with 22 (Invalid argument) for event (ibs_op//).
  /bin/dmesg | grep -i perf may provide additional information.

Output after:

  Error:
  Invalid event (ibs_op//) in per-thread mode, enable system wide with '-a'.

Folowing the suggestion:

  $ sudo perf record -a -e ibs_op// true
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 1.664 MB perf.data (194 samples) ]
  $

Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: João Martins <joao.m.martins@oracle.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Robert Richter <robert.richter@amd.com>
Cc: Sandipan Das <sandipan.das@amd.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20220322221517.2510440-12-eranian@google.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent b58230de

tools/perf/util/evsel.c

+25 −0

Original line number	Diff line number	Diff line
		@@ -2847,9 +2847,23 @@ static bool find_process(const char *name)
		return ret ? false : true;
		}

		static bool is_amd(const char arch, const char cpuid)
		{
		return arch && !strcmp("x86", arch) && cpuid && strstarts(cpuid, "AuthenticAMD");
		}

		static bool is_amd_ibs(struct evsel *evsel)
		{
		return evsel->core.attr.precise_ip
		\|\| (evsel->pmu_name && !strncmp(evsel->pmu_name, "ibs", 3));
		}

		int evsel__open_strerror(struct evsel evsel, struct target target,
		int err, char *msg, size_t size)
		{
		struct perf_env *env = evsel__env(evsel);
		const char *arch = perf_env__arch(env);
		const char *cpuid = perf_env__cpuid(env);
		char sbuf[STRERR_BUFSIZE];
		int printed = 0, enforced = 0;

		@@ -2953,6 +2967,17 @@ int evsel__open_strerror(struct evsel evsel, struct target target,
		return scnprintf(msg, size,
		"Invalid event (%s) in per-thread mode, enable system wide with '-a'.",
		evsel__name(evsel));
		if (is_amd(arch, cpuid)) {
		if (is_amd_ibs(evsel)) {
		if (evsel->core.attr.exclude_kernel)
		return scnprintf(msg, size,
		"AMD IBS can't exclude kernel events. Try running at a higher privilege level.");
		if (!evsel->core.system_wide)
		return scnprintf(msg, size,
		"AMD IBS may only be available in system-wide/per-cpu mode. Try using -a, or -C and workload affinity");
		}
		}

		break;
		case ENODATA:
		return scnprintf(msg, size, "Cannot collect data source with the load latency event alone. "