linux-kernel - Re: [PATCH v6 10/12] perf tools: Improve IBS error handling

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Date:   Tue, 15 Mar 2022 13:15:52 +0530
From:   Ravi Bangoria <ravi.bangoria@....com>
To:     Stephane Eranian <eranian@...gle.com>
Cc:     peterz@...radead.org, kim.phillips@....com, acme@...hat.com,
        jolsa@...hat.com, songliubraving@...com,
        linux-kernel@...r.kernel.org, Ravi Bangoria <ravi.bangoria@....com>
Subject: Re: [PATCH v6 10/12] perf tools: Improve IBS error handling

Stephane,

On 09-Feb-22 2:46 AM, Stephane Eranian wrote:
> From: Kim Phillips <kim.phillips@....com>
> 
> improve the error message returned on failed perf_event_open() on AMD when
> using IBS.
> 
> Output of executing 'perf record -e ibs_op// true' BEFORE this patch:
> 
> 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 cannot 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:
> AMD IBS may only be available in system-wide/per-cpu mode.  Try using -a, or -C and workload affinity

This patch seems to be causing regression to perf python test.

Without this patch:

  $ sudo ./perf test -vvv 19
   19: 'import perf' in python                                         :
  --- start ---
  test child forked, pid 145391
  python usage test: "echo "import sys ; sys.path.append('python'); import perf" | '/usr/bin/python2' "
  test child finished with 0
  ---- end ----
  'import perf' in python: Ok

With this patch:

  $ sudo ./perf test -vvv 19
   19: 'import perf' in python                                         :
  --- start ---
  test child forked, pid 144415
  python usage test: "echo "import sys ; sys.path.append('python'); import perf" | '/usr/bin/python2' "
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  ImportError: python/perf.so: undefined symbol: perf_env__cpuid
  test child finished with -1
  ---- end ----
  'import perf' in python: FAILED!

Thanks,
Ravi