[Bug 1902694] Re: Undetected Data corruption in MPI workloads that use VSX for reductions on POWER9 DD2.1 systems

This bug was fixed in the package linux - 5.8.0-36.40+21.04.1

---------------
linux (5.8.0-36.40+21.04.1) hirsute; urgency=medium

* Packaging resync (LP: #1786013)
- update dkms package versions

[ Ubuntu: 5.8.0-36.40 ]

* debian/scripts/file-downloader does not handle positive failures correctly
(LP: #1878897)
- [Packaging] file-downloader not handling positive failures correctly

[ Ubuntu: 5.8.0-35.39 ]

* Packaging resync (LP: #1786013)
- update dkms package versions
* CVE-2021-1052 // CVE-2021-1053
- [Packaging] NVIDIA -- Add the NVIDIA 460 driver

-- Kleber Sacilotto de Souza <kleber.souza@canonical.com> Thu, 07 Jan
2021 11:57:30 +0100

** Changed in: linux (Ubuntu Hirsute)
Status: In Progress => Fix Released

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2021-1052

** CVE added: https://cve.mitre.org/cgi-bin/cvename.cgi?name=2021-1053

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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:
In Progress
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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