Endianness issue in the VPHN topology update code
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux (Ubuntu) |
Fix Released
|
Undecided
|
Unassigned | ||
Trusty |
Fix Released
|
Medium
|
Chris J Arges | ||
Utopic |
Fix Released
|
Medium
|
Chris J Arges |
Bug Description
SRU Justification:
[Impact]
The current VPHN code assumes the NUMA toplogy updates data are big endian. They are native endian actually since the hypervisor pass them through registers. This has a great performance impact on little endian guests.
[Test Case]
Install NUMA capable power8 machine in LE mode, install LE guest. Measure performance differences in LE guest after applying this patch.
[Fix]
commit 5c9fb1899400096
in v3.18-rc2
A fix has been sent to fix the issue:
http://
Please pick the following commit from Michael Ellermans's tree:
which reads: "powerpc/vphn: NUMA node code expects big-endian"
Now upstream:
commit 5c9fb1899400096
Author: Greg Kurz <email address hidden>
Date: Wed Oct 15 12:42:58 2014 +0200
powerpc/vphn: NUMA node code expects big-endian
tags: | added: architecture-ppc64le bugnameltc-117090 severity-high targetmilestone-inin1404 |
affects: | ubuntu → linux (Ubuntu) |
tags: |
added: targetmilestone-inin14042 removed: targetmilestone-inin1404 |
tags: | added: kernel-da-key |
Changed in linux (Ubuntu): | |
assignee: | nobody → Chris J Arges (arges) |
importance: | Undecided → Medium |
status: | New → In Progress |
Changed in linux (Ubuntu Trusty): | |
assignee: | nobody → Chris J Arges (arges) |
Changed in linux (Ubuntu Utopic): | |
assignee: | nobody → Chris J Arges (arges) |
Changed in linux (Ubuntu Trusty): | |
importance: | Undecided → Medium |
Changed in linux (Ubuntu Utopic): | |
importance: | Undecided → Medium |
status: | New → In Progress |
Changed in linux (Ubuntu Trusty): | |
status: | New → In Progress |
description: | updated |
Changed in linux (Ubuntu): | |
assignee: | Chris J Arges (arges) → nobody |
status: | In Progress → Fix Released |
importance: | Medium → Undecided |
Changed in linux (Ubuntu Utopic): | |
status: | In Progress → Fix Committed |
Changed in linux (Ubuntu Trusty): | |
status: | In Progress → Fix Committed |
tags: | added: verification-done-utopic |
tags: | removed: verification-needed-utopic |
Sent SRU mail to kernel team for 3.13/3.16. Clean cherry-pick and builds fine.