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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Arnaldo Carvalho de Melo <acme@redhat.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Andy Lutomirski <luto@kernel.org>,
        David Ahern <dsahern@gmail.com>, Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Wang Nan <wangnan0@huawei.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.9 207/293] perf evsel: Set attr.exclude_kernel
 when probing max attr.precise_ip
Thread-Topic: [PATCH AUTOSEL for 4.9 207/293] perf evsel: Set
 attr.exclude_kernel when probing max attr.precise_ip
Thread-Index: AQHTz5lHY9sln8VNC0uUfuUwfkHTBg==
Date:   Mon, 9 Apr 2018 00:25:35 +0000
Message-ID: <20180409002239.163177-207-alexander.levin@microsoft.com>
References: <20180409002239.163177-1-alexander.levin@microsoft.com>
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From: Arnaldo Carvalho de Melo <acme@redhat.com>

[ Upstream commit 97365e81366f5ca16a9ce66cff4dd4c5b0d9f4db ]

We should set attr.exclude_kernel when probing for attr.precise_ip
level, otherwise !CAP_SYS_ADMIN users will not default to skidless
samples in capable hardware.

The increase in the paranoid level in commit 0161028b7c8a ("perf/core:
Change the default paranoia level to 2") broke this, fix it by excluding
kernel samples when probing.

Before:

  $ perf record usleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.018 MB perf.data (6 samples) ]
  $ perf evlist -v
  cycles:u: sample_freq: 4000, sample_type: IP|TID|TIME|PERIOD, exclude_ker=
nel: 1

After:

  $ perf record usleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.018 MB perf.data (8 samples) ]
  $ perf evlist -v
  cycles:ppp: sample_freq: 4000, sample_type: IP|TID|TIME|PERIOD, exclude_k=
ernel: 1, precise_ip: 3
                                                                           =
          ^^^^^^^^^^^^^
                                                                           =
          ^^^^^^^^^^^^^
                                                                           =
          ^^^^^^^^^^^^^
  $

To further clarify: we always set .exclude_kernel when non !CAP_SYS_ADMIN
users profile, its just on the attr.precise_ip probing that we weren't doin=
g
so, fix it.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Fixes: 7f8d1ade1b19 ("perf tools: By default use the most precise "cycles" =
hw counter available")
Link: http://lkml.kernel.org/n/tip-t2qttwhbnua62o5gt75cueml@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 tools/perf/util/evsel.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 97fe0c80ff02..1c1291afd6a6 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -258,6 +258,7 @@ struct perf_evsel *perf_evsel__new_cycles(void)
 	struct perf_event_attr attr =3D {
 		.type	=3D PERF_TYPE_HARDWARE,
 		.config	=3D PERF_COUNT_HW_CPU_CYCLES,
+		.exclude_kernel	=3D 1,
 	};
 	struct perf_evsel *evsel;
=20
--=20
2.15.1