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SubjectRe: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option
On Thu, Oct 01, 2015 at 02:33:18AM +0000, 河合英宏 / KAWAI,HIDEHIRO wrote:
> > On Fri, Sep 25, 2015 at 08:28:11PM +0900, Hidehiro Kawai wrote:
> > > This patch introduces new boot option "noextnmi" which disables
> > > external NMI. This option is useful for the dump capture kernel
> > > so that an HA application or administrator wouldn't mistakenly
> > > shoot down the kernel by NMI.
> >
> > So that they can get really stuck when the crash kernel crashes, right?
> > ;-)
>
> No, it is different from my intention.
>
> `mistakenly' in the above means; they issue NMI due to a misconception
> that the monitored host is stuck in the 1st kernel while it is actually
> taking a crash dump in the 2nd kernel. To avoid this kind of accident,
> there is a tool such as fence_kdump which notifies "I'm taking a crash
> dump, so don't send NMI" to the HA clustering software. However, there
> is a time window between kernel panic and the notification.
>
> "noextnmi" allows users to avoid this kind of accident all the time of
> 2nd kernel.

Yes yes, I understand. But if the crash kernel also gets stuck they have
no means of recovery, right? (other than power cycling the hardware)

Just playing devils advocate here, I don't actually object to the patch.


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