Re: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option
From: 'Baoquan He'
Date: Tue Oct 27 2015 - 05:06:39 EST
On 10/27/15 at 09:01am, æåèå / KAWAIïHIDEHIRO wrote:
> > I just have a look at this thread. I am wondering why we don't use
> > existing is_kdump_kernel() directly to disable external NMI if it's
> > in kdump kernel. Then no need to introduce another boot option "noextnmi"
> > which is used only for kdump kernel.
> As I stated in another mail, there is a case where we don't want to
> mask external NMIs in the second kernel. So, we need some
> configurable way. Please see the following quotation.
Got it. Thanks for telling.
> > We souldn't enable this feature silently. Some users wouldn't like
> > to enable this feature. For example, a user enables a watchdog timer
> > which raises an external NMI when the counter is not reset for a
> > specific duration. Then, the second kernel hangs up while saving
> > crash dump, and NMI is delivered to the CPU. The kernel gets panic
> > due to the NMI, prints some information to the display and serial
> > console, and then automatically reboot. In this case, users don't
> > want to block external NMIs.
> Hidehiro Kawai
> Hitachi, Ltd. Research & Development Group
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