linux-kernel - [PATCH] perf test: test case 17 fails on s390 on z/vm

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Date: Tue, 19 Dec 2023 15:32:35 +0100
From: Thomas Richter <tmricht@...ux.ibm.com>
To: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        acme@...nel.org, irogers@...gle.com
Cc: svens@...ux.ibm.com, gor@...ux.ibm.com, sumanthk@...ux.ibm.com,
        hca@...ux.ibm.com, agordeev@...ux.ibm.com,
        Thomas Richter <tmricht@...ux.ibm.com>
Subject: [PATCH] perf test: test case 17 fails on s390 on z/vm

perf test 17 'Setup struct perf_event_attr' fails on s390 z/VM guest,
using linux-next kernel.
Root cause is the fall-back from hardware counter cycles

 perf_event_attr:
  type                             0 (PERF_TYPE_HARDWARE)
  size                             136
  config                           0 (PERF_COUNT_HW_CPU_CYCLES)
  { sample_period, sample_freq }   4000
  sample_type                      IP|TID|TIME|ADDR|PERIOD|DATA_SRC
  read_format                      ID|LOST

which returns -ENOENT on s390 z/VM guest. This causes the code to
fall back to software counter task-clock, as can be seen in the
debug output.
------------------------------------------------------------
 perf_event_attr:
  type                             1 (PERF_TYPE_SOFTWARE)
  size                             136
  config                           0x1 (PERF_COUNT_SW_TASK_CLOCK) <-here
  { sample_period, sample_freq }   4000
  sample_type                      IP|TID|TIME|ADDR|PERIOD|DATA_SRC
  read_format                      ID|LOST

This succeeds on s390 z/VM guest.
This successful installation of the counter task-clock is not listed
in the expected results and the test case fails.

This is caused by commit
commit eb2eac0c7b61 ("perf evsel: Fallback to "task-clock" when not system wide")
which introduced fall back from event 'cycles' to event 'task-clock'.

To fix this on s390 allow event number 0 (cycles) and event number 1
(task-clock) as expected result.

Output before:
 # ./perf test -Fv 17
 17: Setup struct perf_event_attr                                    :
 --- start ---
 running './tests/attr/test-stat-group1'
 unsupp  './tests/attr/test-stat-group1'
 running './tests/attr/test-record-graph-default'
 test limitation '!aarch64'
 excluded architecture list ['aarch64']
 expected config=0, got 1
 FAILED './tests/attr/test-record-graph-default' - match failure
 ---- end ----
 Setup struct perf_event_attr: FAILED!
 #

Output after:
 # ./perf test -F 17
 17: Setup struct perf_event_attr               : Ok
 #

Fixes: eb2eac0c7b61 ("perf evsel: Fallback to "task-clock" when not system wide")
Signed-off-by: Thomas Richter <tmricht@...ux.ibm.com>
---
 tools/perf/tests/attr/base-record | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/tests/attr/base-record b/tools/perf/tests/attr/base-record
index 27c21271a16c..b44e4e6e4443 100644
--- a/tools/perf/tests/attr/base-record
+++ b/tools/perf/tests/attr/base-record
@@ -6,7 +6,7 @@ flags=0|8
 cpu=*
 type=0|1
 size=136
-config=0
+config=0|1
 sample_period=*
 sample_type=263
 read_format=0|4|20
-- 
2.43.0