** Changed in: ubuntu-z-systems
Status: Fix Committed => Fix Released
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https://bugs.launchpad.net/bugs/1847590
Title:
Check for CPU Measurement sampling
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 Disco:
Fix Released
Status in linux source package in Eoan:
Fix Released
Bug description:
SRU Justification:
==================
[Impact]
* Check for CPU Measurement sampling to avoid potential loss of
sampling data
[Fix]
* 932bfc5aae08f3cb20c1c9f051542f5933710151 932bfc5 "s390/cpumsf: Check
for CPU Measurement sampling"
[Test Case]
* Have an LPAR configured with counter and sampling facilities anabled
* Use lscpumf to check the facilities available for your hardware
* Start a benchmark (like mem_alloc) and execute perf top
* Canonical can only do regression testing, functional testing is
currently only doable by IBM
[Regression Potential]
* There is as always some regression potential with having new code in
and other code changed
* but this particular change is limited to the s390x architecture,
* again to the counter and sampling facilities, that need to be
activated by intention
* and is only for compatibility with the latest and newest hw
generation only (z15 and L1III)
[Other Info]
* The fix/patch got upstream accepted with v5.4-rc2, hence it needs to
be applied to E, D and B
* The patch/commit neraly applied cleanly for me on E, D and B except
a little conflict that is easily solveable
* or can even be even automatically be solved by cherry-pick-ing with
'-X theirs'
* This is not relevant for Eoan GA, can be added with the help of an
SRU cycle to Eoan post-GA
__________
Description:
s390/cpumsf: Check for CPU Measurement sampling
s390 IBM z15 introduces a check if the CPU Mesurement Facility
sampling is temporarily unavailable. If this is the case return -EBUSY
and abort the setup of CPU Measuement facility sampling.
Business Value:
With z15 the CPU Measurement sampling facility hardware may be in use when
the Linux kernel CPU Measurement sampling facility device driver sets up
sampling. This results in loss of sampling data and has to be avoided.
With z15 the CPU Measurement facility sampling hardware indicates
being in use and the linux device driver can check for this situation
and can abort any hardware access.
kernel 5.4
Git Commit: 932bfc5aae08f3cb20c1c9f051542f5933710151
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