linux-kernel - Re: [PATCH 1/5] x86, mm, pat: Set WT to PA4 slot of PAT MSR

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Message-ID: <5408C9C4.1010705@zytor.com>
Date:	Thu, 04 Sep 2014 13:21:24 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Toshi Kani <toshi.kani@...com>
CC:	tglx@...utronix.de, mingo@...hat.com, akpm@...uxfoundation.org,
	arnd@...db.de, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	jgross@...e.com, stefan.bader@...onical.com, luto@...capital.net,
	konrad.wilk@...cle.com
Subject: Re: [PATCH 1/5] x86, mm, pat: Set WT to PA4 slot of PAT MSR

On 09/04/2014 01:11 PM, Henrique de Moraes Holschuh wrote:
> 
> I am worried of uncharted territory, here.  I'd actually advocate for not
> enabling the upper four PAT entries on IA-32 at all, unless Windows 9X / XP
> is using them as well.  Is this a real concern, or am I being overly
> cautious?
> 

It is extremely unlikely that we'd have PAT issues in 32-bit mode and
not in 64-bit mode on the same CPU.

As far as I know, the current blacklist rule is very conservative due to
lack of testing more than anything else.

	-hpa

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