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[Leann Ogasawara <leann.ogasawara@xxxxxxxxxxxxx>]

** Changed in: linux (Ubuntu)
     Assignee: (unassigned) => Canonical Kernel Team (canonical-kernel-team)

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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:
  Confirmed

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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