Re: [PATCH] x86: Fix thermal throttling reporting after kexec

[Thomas Gleixner <tglx@linutronix.de>]

On Thu, 1 Oct 2015, Andi Kleen wrote:
> On Thu, Oct 01, 2015 at 11:50:00PM +0200, Andi Kleen wrote:
> > > I see it under the correctness aspect. Mop up before you shut down.
> > 
> > Ok. I suspect if you want to clean up all registers there's much more
> > to do.
> > 
> > BTW there's a small danger in it: if we ever crash accessing on
> > of those registers panic may end up looping.
> 
> I thought more about it. Since this is per logical CPU state
> the cleanup cannot be done in a normal shutdown callback (which
> only runs on one CPU), but needs some kind of global IPI/NMI.
> 
> IPI could deadlock, so it would need to be NMI.
> 
> KVM already has one, but would need to re-organize that into
> first into a generic callback infrastructure.
> 
> I don't think so much change is worth it for this one
> somewhat dubious case. NMI code is also tricky and it's
> probably better to keep the shut down paths as simple
> and reliable as possible. Do you agree?

Yes. Makes sense.

Thanks for analysing it.

	tglx