** Changed in: ubuntu-power-systems
Status: In Progress => Fix Released
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https://bugs.launchpad.net/bugs/1902694
Title:
Undetected Data corruption in MPI workloads that use VSX for
reductions on POWER9 DD2.1 systems
Status in The Ubuntu-power-systems project:
Fix Released
Status in linux package in Ubuntu:
Fix Released
Status in linux source package in Focal:
Fix Released
Status in linux source package in Groovy:
Fix Released
Status in linux source package in Hirsute:
Fix Released
Bug description:
SRU Justification:
[Impact]
* A data integrity issue was observed on POWER 9 (DD2.1) systems.
* It affects Ubuntu 20.04 with kernel 5.4.0-52 and Ubuntu 20.10 with
kernel 5.8.0-26 kernel.
* The root cause is found in the compiling of p9_hmi_special_emu().
* When doing a VMX store (in __get_user_atomic_128_aligned()) to a
buffer (vbuf), the buffer is not 128 bit aligned.
[Fix]
* 1da4a0272c54 "powerpc: Fix undetected data corruption with P9N DD2.1
VSX CI load emulation"
* d1781f237047 "selftests/powerpc: Make alignment handler test P9N
DD2.1 vector CI load workaround"
[Test Case]
* A POWER 9 (DD2.1) bare metal system is needed that has either Ubuntu
20.04, 20.10 or 21.04 installed.
* It's best to test this based on a sample application and test case
"selftests/powerpc: Make alignment handler test P9N DD2.1 vector CI load
workaround"
[Regression Potential]
* The regression risk is relatively moderate, because:
* it only happens with special VSX (vector) instructions in use, e.g.
in p9_hmi_special_emu
* it happens on bare metal only and only on POWER 9 (DD2.1)
* and the changes are very overseeable (in total one effective code
line per patch/commit)
* Since only p9_hmi_special_emu is touched, this will break in case of
any regressions, but this is already broken based on this bug.
[Other]
* According to the reporter this affects Ubuntu 20.04 / 5.4.0-52 and
20.10 / 5.8.0-26.
* Since the development of Hirsute is already open the SRU is
requested for Hirsute, too.
* Patches got upstream accepted in v5.10-rc1 and v5.10-rc2.
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