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

[Thomas Gleixner]

On Wed, 14 Oct 2015, 河合英宏 / KAWAI，HIDEHIRO wrote:
> > On Fri, 25 Sep 2015, 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.
> > >
> > > Currently, only x86 supports this option.
> > 
> > You might add that is can be used for debugging purposes as
> > well. External NMIs can be their own source of trouble. :)
> 
> Thanks for your comments!  I'll do that.
> 
> By the way, I have a pending patch which expands this option like
> this:
> 
> 	apic_extnmi={ bsp | all | none }
> 
> If apic_extnmi=all is specified, external NMIs are broadcast to
> all CPUs.  This raises the successful rate of kernel panic in the case
> where an external NMI to CPU 0 is swallowed by other NMI handlers or
> blocked due to hang-up in NMI context.  The patch works without any
> problems, but I'm going to drop the feature if it will cause long
> discussion.  I'd like to settle this patch set down once.  At least,
> I'm going to change this option to apic_extnmi={bsp|none} style for
> the future expansion.
> 
> How do you think about this?

Do it right away with all three variants. They make a lot of sense to
me.
 
Thanks,

	tglx