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Old 02-10-2011, 12:45 PM
Dave Anderson
 
Default How do debug the kdump kernel using a Xen dump-core file?

----- Original Message -----
> Hello,
>
> 'xm dump-core -L <domain>' generates a coredump of a Xen4 HVM guest, and
> crash is able to poke around in this coredump.
> Thanks for that.
>
> But: How can I use crash to debug the crash/kdump kernel itself?
> I did a 'echo c > /proc/sysrq-trigger' and want to look at the crash
> kernel, not the normal kernel.
>
> Olaf

There is no facility for kdump'ing the secondary "kdump" kernel.

Dave

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Old 02-10-2011, 12:52 PM
Olaf Hering
 
Default How do debug the kdump kernel using a Xen dump-core file?

On Thu, Feb 10, Dave Anderson wrote:

>
>
> ----- Original Message -----
> > Hello,
> >
> > 'xm dump-core -L <domain>' generates a coredump of a Xen4 HVM guest, and
> > crash is able to poke around in this coredump.
> > Thanks for that.
> >
> > But: How can I use crash to debug the crash/kdump kernel itself?
> > I did a 'echo c > /proc/sysrq-trigger' and want to look at the crash
> > kernel, not the normal kernel.
> >
> > Olaf
>
> There is no facility for kdump'ing the secondary "kdump" kernel.

'xm dump-core' can appearently create the required core file while the
kdump kernel runs. Just crash can appearently not "switch over".

What should I modify in crash to let it work from a different "offset",
in other words: the memory reserved for the kdump kernel?

Olaf

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Old 02-10-2011, 01:12 PM
Dave Anderson
 
Default How do debug the kdump kernel using a Xen dump-core file?

----- Original Message -----
>
> 'xm dump-core' can appearently create the required core file while the
> kdump kernel runs. Just crash can appearently not "switch over".
>
> What should I modify in crash to let it work from a different "offset",
> in other words: the memory reserved for the kdump kernel?
>
> Olaf

Ah, I misunderstood. So you are running an HVM guest which has kdump
enabled, the guest has crashed, and now you want to look at the guest's
kdump kernel.

Anyway, like I mentioned in my last message, you *may* be able to coerce
it into running by adding the --machdep physbase=<physical-address> option.
And that would only be possible if it's an x86_64 guest. I'm not sure
what the <physical-address> value should be in that case, so you would
have to experiment.

Normally people don't have much interest in debugging the kdump kernel...

Dave

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