[V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option

河合英宏 / KAWAI,HIDEHIRO hidehiro.kawai.ez at hitachi.com
Tue Oct 27 02:01:15 PDT 2015


> 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.

> 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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