Kernel SRU request submitted:
https://lists.ubuntu.com/archives/kernel-team/2020-August/thread.html#112945
Changing status for Focal and Bionic to 'In Progress'.
** Changed in: linux (Ubuntu Bionic)
Status: New => In Progress
** Changed in: linux (Ubuntu Focal)
Status: New => In Progress
** Changed in: ubuntu-z-systems
Status: Triaged => In Progress
** Description changed:
+ 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.
+ 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.
+ 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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https://bugs.launchpad.net/bugs/1891454
Title:
[UBUNTU 20.04] kernel: s390/cpum_cf,perf: change DFLT_CCERROR counter
name
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