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[Launchpad Bug Tracker <1396235@xxxxxxxxxxxxxxxxxx>]

** Branch linked: lp:ubuntu/trusty-proposed/linux-lts-utopic

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https://bugs.launchpad.net/bugs/1396235

Title:
  Ubuntu - unable to use XMON debugger (running ppc64le on PowerVM)

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]
  Users of LE Power8 hardware might not be able to use XMON properly.

  [Test Case]
  # echo x > /proc/sysrq-trigger
  This should put us in the xmon debugger without errors.

  [Fix]
  3b8a3c01096925a824ed3272601082289d9c23a5 can be cleanly cherry-picked to 3.13/3.16. It only adds cpu_to_be32 macros which shouldn't change the behavior of BE mode CPUs.

  --

  == Comment: #0 - Laurent Dufour <laurent.dufour@xxxxxxxxxx> - 2014-11-25 10:13:17 ==
  ---Problem Description---
  Kernel fails to invoke xmon, instead print following messages

  # echo x > /proc/sysrq-trigger
  [   47.600133] SysRq : Entering xmon
  cpu 0xf: Vector: 0  at [c0000000e8603b80]
      pc: c0000000005610c0: write_sysrq_trigger+0x120/0x260
      lr: c0000000005610c0: write_sysrq_trigger+0x120/0x260
      sp: c0000000e8603ce0
     msr: 8000000000009033
    current = 0xc0000000ef4a0000
    paca    = 0xc000000007df3480   softe: 0        irq_happened: 0x00
      pid   = 2303, comm = bash
  [   47.607247] Bad kernel stack pointer fc7b4b0 at ee27cc4
  cpu 0xf: Vector: 300 (Data Access) at [c000000007f37d40]
      pc: 000000000ee27cc4
      lr: 000000000ee27c44
      sp: fc7b4b0
     msr: 8000000000001000
     dar: 10000000
   dsisr: 42000000
    current = 0xc0000000ef4a0000
    paca    = 0xc000000007df3480   softe: 0        irq_happened: 0x00
      pid   = 2303, comm = bash
  cpu 0xf: Exception 300 (Data Access) in xmon, returning to main loop
  xmon: WARNING: bad recursive fault on cpu 0xf

  ---uname output---
  N/A

  Machine Type = powervm le

  ---System Hang---
   System is hung

  ---Debugger---
  A debugger is not configured

  ---Steps to Reproduce---
   see problem description

  Stack trace output:
   no

  Oops output:
   see problem description

  System Dump Info:
    The system is not configured to capture a system dump.

  This patch has been sent upstream:
  http://patchwork.ozlabs.org/patch/413744/

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