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[Brad Figg <brad.figg@xxxxxxxxxxxxx>]

This bug is missing log files that will aid in diagnosing the problem.
>From a terminal window please run:

apport-collect 1340789

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable
to run this command, please add a comment stating that fact and change
the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the
Ubuntu Kernel Team.

** Changed in: linux (Ubuntu)
       Status: New => Incomplete

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https://bugs.launchpad.net/bugs/1340789

Title:
  Kernel BUG @of/base.c:251 during attach-device operation on Ubuntu
  14.10 LE guest

Status in “linux” package in Ubuntu:
  Incomplete

Bug description:
  -- Problem Description --
  Trying to dynamically add a network device of type virtio to a Ubuntu 14.10 guest running on PowerKVM generates a kernel BUG message. Virsh reports the operation as successful.

  Steps to recreate the problem :

  1) Install 14.10 as a Power KVM guest.
  2) Install ppc64-diag package

  librtas1                  1.3.10-1                     ppc64el      userspace RTAS library
  librtasevent1        1.3.10-1                     ppc64el      RTAS events library
  ppc64-diag           2.6.6-0ubuntu1               ppc64el      Platform error log analysis tool and rtas_errd daemon
  libservicelog-1.1-1:ppc64el        1.1.14-0ubuntu1              ppc64el      Library to create and maintain a database for storing events
  servicelog             1.1.12-0ubuntu1              ppc64el      Platform Service/Error Message Database

  3) Using a network device definition as mentioned below try a virsh
  attach-device operation

  On the PowerKVM host :

  # cat net
  <interface type='bridge'>
     <mac address='52:54:00:A0:9D:9a'/>
     <source bridge='virbr0'/>
     <model type='virtio'/>
  </interface>

  # virsh attach-device ss_1410_1 net
  Device attached successfully

  #

  Following kernel BUG is observed on the guest

  [ 6380.112079] RTAS: event: 1, Type: Unknown, Severity: 1
  [ 6380.209844] ------------[ cut here ]------------
  [ 6380.209848] kernel BUG at /build/buildd/linux-3.15.0/drivers/of/base.c:251!
  [ 6380.209922] Oops: Exception in kernel mode, sig: 5 [#1]
  [ 6380.209963] SMP NR_CPUS=2048 NUMA pSeries
  [ 6380.210006] Modules linked in: pseries_rng rtc_generic e1000
  [ 6380.210084] CPU: 0 PID: 3642 Comm: drmgr Not tainted 3.15.0-6-generic #11-Ubuntu
  [ 6380.210146] task: c0000000770968a0 ti: c000000079858000 task.ti: c000000079858000
  [ 6380.210207] NIP: c000000000871c24 LR: c000000000872704 CTR: c000000000080ed0
  [ 6380.210268] REGS: c00000007985b7f0 TRAP: 0700   Not tainted  (3.15.0-6-generic)
  [ 6380.210328] MSR: 8000000000029033 <SF,EE,ME,IR,DR,RI,LE>  CR: 24002488  XER: 20000000
  [ 6380.210473] CFAR: c000000000872700 SOFTE: 1 
  [ 6380.210473] GPR00: c000000000872704 c00000007985ba70 c000000001791188 c000000004192100 
  [ 6380.210473] GPR04: 0000000000000001 c00000007e039fc0 c00000000419ee80 c000000001aa1188 
  [ 6380.210473] GPR08: 0000000000000002 0000000000000001 0000000000000000 c00000000453025b 
  [ 6380.210473] GPR12: 0000000024002482 c00000000fe40000 0000000000000000 000000000000000c 
  [ 6380.210473] GPR16: 000001001e42eeda 0000000000000020 0000000000000000 0000000010016a00 
  [ 6380.210473] GPR20: 0000000010016950 00000000100167b0 0000000000000001 c00000007e039800 
  [ 6380.210473] GPR24: c000000000cc0310 c000000004530009 c000000077594f80 c00000007fff6d38 
  [ 6380.210473] GPR28: 0000000000000015 c000000004192100 c000000001aa01b0 c000000004192100 
  [ 6380.211355] NIP [c000000000871c24] .of_node_add+0x34/0x110
  [ 6380.211397] LR [c000000000872704] .of_attach_node+0xd4/0xf0
  [ 6380.211440] Call Trace:
  [ 6380.211462] [c00000007985ba70] [0000000010016950] 0x10016950 (unreliable)
  [ 6380.211525] [c00000007985baf0] [c000000000872704] .of_attach_node+0xd4/0xf0
  [ 6380.211633] [c00000007985bb70] [c000000000076420] .ofdt_write+0x590/0x780
  [ 6380.211753] [c00000007985bc50] [c00000000030727c] .proc_reg_write+0xac/0x110
  [ 6380.211815] [c00000007985bcf0] [c000000000279370] .vfs_write+0xe0/0x260
  [ 6380.211876] [c00000007985bd90] [c00000000027a034] .SyS_write+0x64/0x110
  [ 6380.211939] [c00000007985be30] [c000000000009ffc] syscall_exit+0x0/0x7c
  [ 6380.212001] Instruction dump:
  [ 6380.212033] fbc1fff0 fbe1fff8 f8010010 f821ff81 7c7f1b78 60000000 60000000 2fbf0000 
  [ 6380.212142] 419e006c 813f0094 69290001 792907e0 <0b090000> 3fc2ffeb 3bdefe60 7fc3f378 
  [ 6380.212250] ---[ end trace 410b60b95ac50ef5 ]---
  [ 6380.214151] 
  sachin@1410:/var/log$ 

  sachin@1410:/var/log$ cat /etc/issue
  Ubuntu Utopic Unicorn (development branch) \n \l

  sachin@1410:/var/log$ uname -a
  Linux 1410 3.15.0-6-generic #11-Ubuntu SMP Thu Jun 12 00:40:49 UTC 2014 ppc64le ppc64le ppc64le GNU/Linux
  sachin@1410:/var/log$

  The BUG_ON() it is hitting is likely this one:

  int of_node_add(struct device_node *np)
  {
  	int rc = 0;

          BUG_ON(!of_node_is_initialized(np));

  This appears to be related to commit
  75b57ecf9d1d1e17d099ab13b8f48e6e038676be.

  This was part of the updates that Grant did to move the device tree
  from /proc/to sysfs. As part of this he removed the kref_init call we
  made prior to adding the device node.

  Attached patch "powerpc/pseries: dynamically added OF nodes need to
  call of_node_init"

  With the attach patch, the attach/detach device operation works
  correctly. No kernel BUG is observed.

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