[SRU][F][PATCH 0/1] s390/cpum_cf: Add new extended counters for IBM z15 (LP: 1881096)

[frank.heimes at canonical.com]

Buglink: https://bugs.launchpad.net/bugs/1881096

SRU Justification:

[Impact]

* With perf from Ubuntu 20.04 on IBM z15 hardware, some counters reported with lscpumf are not usable with 'perf stat -e'.

* 'lscpumf -c' provides a list of available counters, but the following are not usable: DFLT_ACCESS, DFLT_CYCLES, DFLT_CC, DFLT_CCERROR

* 'perf list' is also not offering these counters.

* On the kernel side this is fixed with the following upstream accepted commit:

[Fix]

* d68d5d51dc898895b4e15bea52e5668ca9e76180 d68d5d51dc898895b "s390/cpum_cf: Add new extended counters for IBM z15"

[Test Case]

* Requires the fix/patch of the perf tool, as mentioned in the bug, too.

* An IBM z15 (or LinuxONE III) system with Ubuntu 20.04 installed in LPAR is needed where the counters are enabled in the activation profile.

* Use 'perf list' to determine if the counters DFLT_ACCESS, DFLT_CYCLES, DFLT_CC, DFLT_CCERROR are listed

* Use 'perf stat -e' to enable amd make use of these counters.

[Regression Potential]

* The regression can be considered as low, since:

* it's architecture specific (s390x)

* limited to IBM z15 hardware

* and only additional (s390x) hardware counters are defined and added.

[Other]

* This requires a patch to be included into the perf itself, too - please see bug description for more details.

* Since this patch is upstream in kernel 5.7 it will automatically land in groovy.

Thomas Richter (1):
  From: Thomas Richter <tmricht at linux.ibm.com>

 arch/s390/kernel/perf_cpum_cf_events.c | 123 ++++++++++++++++++++++++-
 1 file changed, 122 insertions(+), 1 deletion(-)

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2.25.1