[Xen-devel] Re: dom0 pvops crash apparently due to guest migration

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Jeremy Fitzhardinge writes ("Re: dom0 pvops crash apparently due to guest 
migration"):
> On 11/29/2010 03:59 AM, Ian Jackson wrote:
> > One of my test boxes encountered the crash whose oops you see below.
> > It doesn't do it every time, or even every time on this machine (since
> > the credit2 test in the same run worked).  The crash seems to have
> > occurred just at the end of the migration of a PV guest.
> 
> Do you have a feel for what the likelihood of failure is?  Has this
> started happening recently?

The probability of failure seems reasonably high.  This is a different
test machine so it is possible that there is something wrong with the
hardware, but all of the tests with the XCP kernel work fine.

> Hm, I'm still not really sure why alloc_vm_area() does a
> vmalloc_sync_all in the first place...  But that BUG shouldn't happen
> regardless.

It's not just blkback; here's one that shows a call trace with netback
instead:

 ------------[ cut here ]------------
 kernel BUG at arch/x86/mm/fault.c:210!
 invalid opcode: 0000 [#1] SMP 
 last sysfs file: 
/sys/devices/virtual/net/xenbr0/bridge/topology_change_detected
 Modules linked in: e1000e [last unloaded: scsi_wait_scan]
 
 Pid: 22, comm: xenwatch Not tainted (2.6.32.26 #1)         
 EIP: 0061:[<c104c058>] EFLAGS: 00010086 CPU: 0
 EIP is at vmalloc_sync_one+0x118/0x128
 EAX: 00088480 EBX: 04424067 ECX: ffffffe0 EDX: 7c83ffff
 ESI: 00000000 EDI: c182ae00 EBP: dfcdbeb0 ESP: dfcdbe8c
  DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0069
 Process xenwatch (pid: 22, ti=dfcda000 task=dfccc510 task.ti=dfcda000)
 Stack:
  dff99c44 00cdbeb0 00000000 c568f800 dff99c44 7c83ffff f8000000 c568f800
 <0> dff99c44 dfcdbed0 c104ca9a c182ae00 c1780204 c445d600 cd034dc0 c445d600
 <0> c445d620 dfcdbedc c10df14a fffffff4 dfcdbf34 c1236b30 00000301 00000300
 Call Trace:
  [<c104ca9a>] ? vmalloc_sync_all+0x5c/0xbe
  [<c10df14a>] ? alloc_vm_area+0x44/0x4b
  [<c1236b30>] ? netif_map+0x2d/0x2e3
  [<c10e95c8>] ? kfree+0x111/0x119
  [<c1229291>] ? xenbus_scanf+0x38/0x4b
  [<c1229291>] ? xenbus_scanf+0x38/0x4b
  [<c12361fa>] ? frontend_changed+0x2c3/0x526
  [<c1229b39>] ? xenbus_otherend_changed+0x5c/0x61
  [<c1229c97>] ? frontend_changed+0xa/0xd
  [<c1228783>] ? xenwatch_thread+0xf6/0x11e
  [<c10795df>] ? autoremove_wake_function+0x0/0x33
  [<c122868d>] ? xenwatch_thread+0x0/0x11e
  [<c1079397>] ? kthread+0x61/0x66
  [<c1079336>] ? kthread+0x0/0x66
  [<c1030dd7>] ? kernel_thread_helper+0x7/0x10
 Code: eb fe 89 d8 89 f2 ff 15 08 7d 68 c1 89 d6 8b 55 f0 89 c3 89 c8 0f ac d0 
0c 89 c1 89 d8 0f ac f0 0c c1 e1 05 c1 e0 05 39 c1 74 06 <0f> 0b eb fe 31 ff 83 
c4 18 89 f8 5b 5e 5f 5d c3 55 89 e5 56 53 
 EIP: [<c104c058>] vmalloc_sync_one+0x118/0x128 SS:ESP 0069:dfcdbe8c
 ---[ end trace 008e317122f8c510 ]---

Ian.

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