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[Andy Whitcroft <apw@xxxxxxxxxxxxx>]

** Changed in: linux (Ubuntu Utopic)
       Status: In Progress => Fix Committed

** Changed in: linux (Ubuntu Trusty)
       Status: In Progress => Fix Committed

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https://bugs.launchpad.net/bugs/1401150

Title:
  Endianness issue in the VPHN topology update code

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Trusty:
  Fix Committed
Status in linux source package in Utopic:
  Fix Committed

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 5c9fb1899400096c6818181c525897a31d57e488 upstream
  in v3.18-rc2

  A fix has been sent to fix the issue:

  http://patchwork.ozlabs.org/patch/396171/

  Please pick the following commit from Michael Ellermans's tree:

  http://git.kernel.org/cgit/linux/kernel/git/mpe/linux.git/commit/?id=5c9fb1899400096c6818181c525897a31d57e488

  which reads: "powerpc/vphn: NUMA node code expects big-endian"

  Now upstream:

  commit 5c9fb1899400096c6818181c525897a31d57e488
  Author: Greg Kurz <gkurz@xxxxxxxxxxxxxxxxxx>
  Date:   Wed Oct 15 12:42:58 2014 +0200

      powerpc/vphn: NUMA node code expects big-endian

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