Re: [Xen-devel] kernel BUG at arch/x86/xen/mmu.c:1860!

[Christophe Saout <christophe@xxxxxxxx>]

Hi again,

> > >      > While doing LVM snapshot for migration and get the following:
> > >      >
> > >      > Dec 26 15:58:29 xen01 kernel: ------------[ cut here ]------------
> > >      > Dec 26 15:58:29 xen01 kernel: kernel BUG at 
> > > arch/x86/xen/mmu.c:1860!
> > >      > Dec 26 15:58:29 xen01 kernel: invalid opcode: 0000 [#1] SMP
> > >      > Dec 26 15:58:29 xen01 kernel: last sysfs file: /sys/block/dm-26/dev
> > >      > Dec 26 15:58:29 xen01 kernel: CPU 0
> > >      > Dec 26 15:58:29 xen01 kernel: Modules linked in: ipt_MASQUERADE
> >
> > It would be very good to track this down and get it fixed.. 
> > hopefully you're able to help a bit and try some things to debug it.
> > 
> > Konrad maybe has some ideas to try.. 
> 
> I am seeing this with an lvcreate here, so I guess it's somehow related
> to device-mapper stuff in general.
> 
> It doesn't look like this has been resolved yet.  Somewhere I saw a
> request for the hypervisor message related to the pinning failure.
> 
> Here it is:
> 
> (XEN) mm.c:2364:d0 Bad type (saw 7400000000000001 != exp 1000000000000000) 
> for mfn 41114f (pfn d514f)
> (XEN) mm.c:2733:d0 Error while pinning mfn 41114f
> 
> I have a bit of experience in debugging things, so if I can help someone
> with more information...

Additional information: This happened with a number of commands now.
However, I am running a multipath setup and every time the crash seemed
to be caused in the process context of the multipath daemon.  I think
the daemon listens to events from the device-mapper subsystem to watch
for changes and the problem somehow arises from there, since on another
machine with the same XEN/Dom0 version without such a daemon I never had
any troubles with LVM.

 [<ffffffff810052e2>] pin_pagetable_pfn+0x52/0x60    
 [<ffffffff81006f5c>] xen_alloc_ptpage+0x9c/0xa0
 [<ffffffff81006f8e>] xen_alloc_pte+0xe/0x10
 [<ffffffff810decde>] __pte_alloc+0x7e/0xf0
 [<ffffffff810e15c5>] handle_mm_fault+0x855/0x930
 [<ffffffff8102dd9e>] ? pvclock_clocksource_read+0x4e/0x100
 [<ffffffff810e734c>] ? do_mmap_pgoff+0x33c/0x380
 [<ffffffff81452b96>] do_page_fault+0x116/0x3e0
 [<ffffffff8144ff65>] page_fault+0x25/0x30

Cheers,
        Christophe



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