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Date: Sun, 10 May 2009 10:55:36 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Alan Cox <alan@lxorguk.ukuu.org.uk>
CC: Keir Fraser <keir.fraser@eu.citrix.com>,
       Ian Campbell <Ian.Campbell@eu.citrix.com>,
       Jeremy Fitzhardinge <jeremy@goop.org>,
       the arch/x86 maintainers <x86@kernel.org>,
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Subject: Re: [Xen-devel] Re: [PATCH 06/16] xen: disable PAT
References: <4A05CD29.6050505@zytor.com>	<C62C5B3C.AB1A%keir.fraser@eu.citrix.com> <20090510142928.66bb57bb@lxorguk.ukuu.org.uk>
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Alan Cox wrote:
> 
> There are quite a few different CPUs with PAT errata. I've no idea why
> there are so many errata about that specific bit.
> 

I suspect it is simply because:

a) it moves around between the various page table formats;
b) the default configuration and existing OSes don't use it;
c) it isn't even *present* in some formats.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.