Check for CPU Measurement sampling
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
Ubuntu on IBM z Systems |
Fix Released
|
Medium
|
Frank Heimes | ||
linux (Ubuntu) |
Fix Released
|
Undecided
|
Skipper Bug Screeners | ||
Bionic |
Fix Released
|
Undecided
|
Unassigned | ||
Disco |
Fix Released
|
Undecided
|
Unassigned | ||
Eoan |
Fix Released
|
Undecided
|
Skipper Bug Screeners |
Bug Description
SRU Justification:
==================
[Impact]
* Check for CPU Measurement sampling to avoid potential loss of sampling data
[Fix]
* 932bfc5aae08f3c
[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: 932bfc5aae08f3c
tags: | added: architecture-s39064 bugnameltc-181842 severity-high targetmilestone-inin1910 |
Changed in ubuntu: | |
assignee: | nobody → Skipper Bug Screeners (skipper-screen-team) |
affects: | ubuntu → linux (Ubuntu) |
Changed in ubuntu-z-systems: | |
status: | New → Triaged |
importance: | Undecided → Medium |
tags: | added: s390x |
Changed in linux (Ubuntu Bionic): | |
status: | New → Fix Committed |
Changed in linux (Ubuntu Disco): | |
status: | New → Fix Committed |
Changed in linux (Ubuntu Eoan): | |
status: | In Progress → Fix Committed |
Changed in ubuntu-z-systems: | |
status: | In Progress → Fix Committed |
Changed in ubuntu-z-systems: | |
status: | Fix Committed → Fix Released |
------- Comment From <email address hidden> 2019-10-10 10:08 EDT-------
This will also be requested for 19.04, and 18.04.
Patches will be provided if required for these dedicated kernels.