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

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Date:	Sun, 11 Oct 2015 21:37:40 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andi Kleen <ak@...ux.intel.com>
cc:	Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Fix thermal throttling reporting after kexec

Andi,

On Fri, 2 Oct 2015, Thomas Gleixner wrote:
> 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.

I wanted to pick this up, but then I noticed that it actually belongs
to X86 MCE INFRASTRUCTURE which is maintained by Tony and Borislav.

Can you please resend to them? It would be nice if you could add the
discussion about not cleaning it up in the changelog.

Thanks and sorry for noticing so late,

       tglx
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