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Date: Thu, 16 Feb 2012 16:56:03 -0500
From: Don Zickus <dzickus@redhat.com>
Subject: Re: [tip:x86/debug] x86/kdump: No need to disable ioapic/ lapic in
 crash path
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To: Yinghai Lu <yinghai@kernel.org>
Cc: linux-tip-commits@vger.kernel.org, mingo@elte.hu, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, mingo@redhat.com, "Eric W. Biederman" <ebiederm@xmission.com>, hpa@zytor.com, akpm@linux-foundation.org, torvalds@linux-foundation.org, tglx@linutronix.de, vgoyal@redhat.com

On Thu, Feb 16, 2012 at 01:53:29PM -0800, Yinghai Lu wrote:
> On Thu, Feb 16, 2012 at 9:27 AM, Don Zickus <dzickus@redhat.com> wrote:
> =

> > So I think I figured it out. =A0I went through and commented out code in
> > disable_local_APIC until I narrowed it down to the piece of code that
> > needs to be disabled for it to work.
> >
> > Surprise, surprise... its LVTPC or perf! :-) =A0Actually it is the
> > nmi_watchdog which uses perf. =A0My theory is NMIs are not disabled and=
 one
> > is generated by the local apic during decompression (just bad timing) a=
nd
> > *splat*.
> >
> > Yinghai, you can probably prove this by
> >
> > echo 0 > /proc/sys/kernel/nmi_watchdog
> >
> > then do your kdump crash test.
> =

> yes.  that will make kdump crash working.

Cool.  Thanks.

Eric,

Just let me know how you want to handle disabling NMIs in the kexec in
panic shutdown case.

Cheers,
Don

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