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

[æåèå / KAWAIïHIDEHIRO]

> On Thu, Oct 01, 2015 at 10:24:19AM +0000, æåèå / KAWAIïHIDEHIRO wrote:
> > But how do we check if the starting kernel is a dump capture kernel?
> 
> How does that first kernel pass info to the capture kernel?

As I described in the previous mail, You just have to add "noextnmi"
to KDUMP_COMMANDLINE_APPEND in /etc/sysconfig/kdump.  Then, "noextnmi"
option is passed to the capture kernel by the action of kexec command.

Cmdline option gives users flexibility.  I'm not sure all users
want to disable external NMIs in the 2nd kernel.

> > I think using cmdline option is the simplest way.
> 
> More often than not, simplest != correct.
> 
> What happens if I pass this option to the first kernel? All of a sudden
> my *first* kernel doesn't get external NMIs.

Yes, your first kernel doesn't get external NMIs, but basically
you don't have to set "noextnmi" option to the first kernel.


Hidehiro Kawai
Hitachi, Ltd. Research & Development Group