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Re: [Xen-devel] Xen 3.2.0 crash: Pagetable walk


  • To: "Christopher S. Aker" <caker@xxxxxxxxxxxx>
  • From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
  • Date: Wed, 05 Mar 2008 09:57:53 +0000
  • Cc: xen devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Wed, 05 Mar 2008 01:59:13 -0800
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: Ach+p2Dgn22nxOqaEdyBAAAX8io7RQ==
  • Thread-topic: [Xen-devel] Xen 3.2.0 crash: Pagetable walk

Thanks,

This host crash is fixed (in xen-unstable, and I will backport to 3.2
branch) -- we are doing a mfn-to-pfn translation lookup on an unvalidated
mfn. In fact the 'mfn' is not a frame number at all. It's (legitimately)
garbage; probably a Linux swap_pte.

Of course this doesn't explain why your guest crashed in the first place,
apart from the obvuous that it dereferenced a not-present page, but at least
in 3.2.1 it will be just a guest crash. Not a host crash!

 -- Keir

On 5/3/08 04:32, "Christopher S. Aker" <caker@xxxxxxxxxxxx> wrote:

> Thanks for the explanation -- interesting stuff :)
> 
>> How much memory does this machine have?
> 
> total_memory           : 24574
> 
>> Do you have the xen-syms file associated with this crash dump?
>> It may shed some light. Mail it to me privately or stick it
>> somewhere for download if possible.
> 
> http://www.linode.com/~caker/xen/BUGshow_page_walk/
> 
> Thanks,
> -Chris



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