APPLIED: [SRU][B][PATCH v3 0/1] kernel: s390/cpum_cf, perf: change DFLT_CCERROR counter name (LP: 1891454)

[Khaled Elmously]

On 2020-08-28 12:55:05 , frank.heimes at canonical.com wrote:
> Buglink: https://bugs.launchpad.net/bugs/1891454
> 
> SRU Justification:
> 
> [Impact]
> 
> * Add/change the counter name DLFT_CCERROR to DLFT_CCFINISH on IBM z15 to avoid confusion.
> 
> * This counter counts completed DEFLATE instructions with exit code 0, 1 or 2.
> 
> * And since exit code 0 means success and exit code 1 or 2 indicate errors the name can be ambiguous.
> 
> [Fix]
> 
> * Add new extended counters for IBM z15
> 
> * Backport Bionic: https://launchpadlibrarian.net/493439681/u18-0001-s390-cpum_cf-Add-new-extended-counters-for-IBM-z15.patch
> 
> [Test Case]
> 
> * Enable hardware counters in the activation profile of a z15 LPAR.
> 
> * Just check the countername in sysfs with: ls /sys/devices/cpum_cf/events/{DFLT_CCERROR,DFLT_CCFINISH}
> 
> [Regression Potential] 
> 
> * The regression potential can be considered as low, since:
> 
> * Counters like these are usually not activated by default and need to be explicitly enabled.
> 
> * No code functionality is changed with that patch, only a renaming is done at 3 places in one code file arch/s390/kernel/perf_cpum_cf_events.c as well as in /tools/perf/pmu-events/arch/s390/cf_z15/extended.json.
> 
> * The fix got already upstream accepted in 5.8-rc7, hence it got upstream reviewed,
> 
> * and the modifications are limited to s390x, are only relevant for the z15 / LinuxONE III hw generation that are relatively new.
> 
> * Issue with the renaming I can think of are that people don't know about the new name and may look for the old one and don't find it anymore,
> 
> * and with that also if the old counter name is used in scripts or applications, these may fails due to an unknown counter name.
> 
> Thomas Richter (1):
>   s390/cpum_cf: Add new extended counters for IBM z15
> 
>  arch/s390/kernel/perf_cpum_cf_events.c | 123 ++++++++++++++++++++++++-
>  1 file changed, 122 insertions(+), 1 deletion(-)
> 
> -- 
> 2.25.1
> 
> 
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