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

["'Baoquan He'" <bhe@redhat.com>]

On 10/27/15 at 09:01am, 河合英宏 / KAWAI，HIDEHIRO wrote:
> Hi,
> 
> > 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.
> 
> Regards,
> 
> Hidehiro Kawai
> Hitachi, Ltd. Research & Development Group
> 
>