linux-kernel - Re: 2.6.18-rc6-mm1: GPF loop on early boot

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Message-ID: <45051330.5050205@goop.org>
Date:	Mon, 11 Sep 2006 00:41:36 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Andrew Morton <akpm@...l.org>, Andi Kleen <ak@...e.de>,
	Laurent Riffard <laurent.riffard@...e.fr>,
	Arjan van de Ven <arjan@...radead.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Jeremy Fitzhardinge <jeremy@...source.com>
Subject: Re: 2.6.18-rc6-mm1: GPF loop on early boot

Ingo Molnar wrote:
> because userspace does not use it normally, while with %gs we'd switch 
> between glibc's descriptor [which must be shadowed by the CPU] and the 
> kernel's descriptor [which must be shadowed by the CPU too] - hence 
> causing a constant reloading of the shadow register.
>   

Well, that means the only operation which would be different would be 
the pop %fs at the end, since only it would end up loading a null 
selector.  All the other operations would presumably take just as long.

    J
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