Date: Wed, 14 Jul 2010 23:31:10 +0100 (BST)
From: "Maciej W. Rozycki" <macro@linux-mips.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@elte.hu>,
        Peter Zijlstra <peterz@infradead.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Steven Rostedt <rostedt@rostedt.homelinux.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>, Christoph Hellwig <hch@lst.de>,
        Li Zefan <lizf@cn.fujitsu.com>, Lai Jiangshan <laijs@cn.fujitsu.com>,
        Johannes Berg <johannes.berg@intel.com>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Arnaldo Carvalho de Melo <acme@infradead.org>,
        Tom Zanussi <tzanussi@gmail.com>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Andi Kleen <andi@firstfloor.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Jeremy Fitzhardinge <jeremy@goop.org>,
        "Frank Ch. Eigler" <fche@redhat.com>, Tejun Heo <htejun@gmail.com>
Subject: Re: [patch 1/2] x86_64 page fault NMI-safe
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On Wed, 14 Jul 2010, Linus Torvalds wrote:

> You just count differently. I don't count the first one (the "real"
> NMI). That obviously happens. So I only count how many interrupts we
> need to fake. That's my "one". That's the one that happens as a result
> of the fault that we take on the iret in the emulated model.

 Ah, I see -- so we are on the same page after all.

> (Yeah, yeah, you can call it a "one-bit counter", but I don't think
> that's a counter. It's just a bit of information).

 Hardware has something like a strapped-high D flip-flop (NMI goes to the 
clock input) with an extra reset input I presume -- this dates back to 
8086 when the transistor count mattered with accuracy higher than 1e6. ;)

  Maciej
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