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Message-ID: <480CADD3.3010209@zytor.com>
Date: Mon, 21 Apr 2008 11:08:03 -0400
From: "H. Peter Anvin" <hpa@...or.com>
To: Mathieu Desnoyers <compudj@...stal.dyndns.org>
CC: Pavel Machek <pavel@....cz>, mingo@...e.hu, akpm@...l.org,
Jeremy Fitzhardinge <jeremy@...p.org>,
Steven Rostedt <rostedt@...dmis.org>,
"Frank Ch. Eigler" <fche@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] x86 NMI-safe INT3 and Page Fault (v5)
Mathieu Desnoyers wrote:
>
> Just to be clear : the added cost on normal interrupt return is to add a
> supplementary test of the thread flags already loaded in registers and
> a conditional branch. This is used to detect if we are nested over an
> NMI handler. I doubt anyone ever notice an impact caused by this added
> test/branch.
>
Why the **** would you do this except in the handful of places where you
actually *could* be nested over an NMI handler (basically #MC, #DB and
INT3)?
-hpa
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