[Bug 1891454] Comment bridged from LTC Bugzilla

------- Comment From heinz-werner_seeck@de.ibm.com 2020-10-20 08:52 EDT-------
IBM Bugzilla status->closed, Fix Released with all requested distros

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https://bugs.launchpad.net/bugs/1891454

Title:
[UBUNTU 20.04] kernel: s390/cpum_cf,perf: changeDFLT_CCERROR counter
name

Status in Ubuntu on IBM z Systems:
Fix Released
Status in linux package in Ubuntu:
Fix Released
Status in linux source package in Bionic:
Fix Released
Status in linux source package in Focal:
Fix Released
Status in linux source package in Groovy:
Fix Released

Bug description:
SRU Justification:
==================

[Impact]

* 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]

* Rename s390 z15 counter named DFLT_CCERROR to DFLT_CCFINISH.

* Backport Focal: https://launchpadlibrarian.net/493272507/0001-s390
-cpum_cf-perf-change-DFLT_CCERROR-counter-name.patch

* 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.

[Other Info]

* The backports are based on commit
3d3af181d370069861a3be94608464e2ff3682e2 ("s390/cpum_cf,perf: change
DFLT_CCERROR counter name") that is upstream accepted since v5.8-rc7.

* Hence this SRU is not requested for groovy, since it's already in groovys kernel 5.8 in proposed, but only requested for focal and bionic.
__________

Description: kernel: s390/cpum_cf,perf: change DFLT_CCERROR counter name
Symptom: Counter name CCERROR is misleading.
Problem: Change the counter name DLFT_CCERROR to DLFT_CCFINISH on
               IBM z15. This counter counts completed DEFLATE instructions
               with exit code 0, 1 or 2. Since exit code 0 means success
               and exit code 1 or 2 indicate errors, change the counter
               name to avoid confusion. This counter is incremented each
               time the DEFLATE instruction completed regardless if an
               error was detected or not.
Solution: Rename s390 z15 counter named DFLT_CCERROR to DFLT_CCFINISH
Reproduction: Command # ls /sys/devices/cpum_cf/events/DFLT_CCERROR
               currently succeeds. After this patch has been applied the
               command does not work anymore. The file does not exist
               anymore. Use command
               # ls /sys/devices/cpum_cf/events/DFLT_CCFINISH
               instead.
Upstream-ID: 5ce1a24dd98c00a57a8fa13660648abf7e08e3ef
Component: kernel 5.8

Will be integrated into 20.10 by kernel 5.8 integration.

Backport available for 20.04.
To be checked for 18.04 and 16.04, update will be provided

Here is the backported patch.
The upstream commit id is 3d3af181d370069861a3be94608464e2ff3682e2
("s390/cpum_cf,perf: change DFLT_CCERROR counter name")

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