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Date: Wed, 14 Sep 2011 08:49:17 -0400
From: Don Zickus <dzickus@redhat.com>
To: Avi Kivity <avi@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>, Jeremy Fitzhardinge <jeremy@goop.org>,
        Peter Zijlstra <peterz@infradead.org>,
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        Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Subject: Re: [PATCH 08/13] xen/pvticketlock: disable interrupts while blocking
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On Wed, Sep 14, 2011 at 10:00:07AM +0300, Avi Kivity wrote:
> On 09/13/2011 10:21 PM, Don Zickus wrote:
> >Or are you saying an NMI in an idle system will have the same %rip thus
> >falsely detecting a back-to-back NMI?
> >
> >
> 
> That's easy to avoid - insert an instruction zeroing the last
> nmi_rip somewhere before or after hlt.  It's always okay to execute
> such an instruction (outside the nmi handler itself), since nmi_rip
> is meant to detect a "no instructions executed" condition.

Ah. Like a touch_nmi_watchdog() type of thing.  Interesting.  I'll poke
around the idle code.  Need to instrument a reproducer first.

Thanks,
Don