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

[Andi Kleen <ak@linux.intel.com>]

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?

-Andi

-- 
ak@linux.intel.com -- Speaking for myself only