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

From	Thomas Gleixner <tglx@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH] x86: Fix thermal throttling reporting after kexec
Date	2015-10-02 22:40 +0200
Message-ID	<qffhv-5Ni-3@gated-at.bofh.it> (permalink)
References	(1 earlier) <qeL06-3Kc-13@gated-at.bofh.it> <qePQ6-2MU-15@gated-at.bofh.it> <qeTTI-eK-21@gated-at.bofh.it> <qeU3o-qz-9@gated-at.bofh.it> <qeUd4-Rt-31@gated-at.bofh.it>
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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
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[PATCH] x86: Fix thermal throttling reporting after kexec Andi Kleen <andi@firstfloor.org> - 2015-09-24 22:20 +0200
  Re: [PATCH] x86: Fix thermal throttling reporting after kexec Thomas Gleixner <tglx@linutronix.de> - 2015-10-01 14:20 +0200
    Re: [PATCH] x86: Fix thermal throttling reporting after kexec Andi Kleen <ak@linux.intel.com> - 2015-10-01 19:30 +0200
      Re: [PATCH] x86: Fix thermal throttling reporting after kexec Thomas Gleixner <tglx@linutronix.de> - 2015-10-01 23:50 +0200
        Re: [PATCH] x86: Fix thermal throttling reporting after kexec Andi Kleen <andi@firstfloor.org> - 2015-10-02 00:00 +0200
          Re: [PATCH] x86: Fix thermal throttling reporting after kexec Andi Kleen <ak@linux.intel.com> - 2015-10-02 00:10 +0200
            Re: [PATCH] x86: Fix thermal throttling reporting after kexec Thomas Gleixner <tglx@linutronix.de> - 2015-10-02 22:40 +0200

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