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From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Andi Kleen <andi@firstfloor.org>,
	tglx@linutronix.de, linux-kernel@vger.kernel.org
Subject: Folding _PAGE_PWT into _PAGE_PCD (was Re: unify pagetable accessors patch causes double fault II)
Date: Tue, 15 Jan 2008 09:16:50 -0800	[thread overview]
Message-ID: <478CEA82.9010606@goop.org> (raw)
In-Reply-To: <20080115135317.GA13493@elte.hu>

Ingo Molnar wrote:
> -#define _PAGE_PRESENT	(_AC(1, UL)<<_PAGE_BIT_PRESENT)
> -#define _PAGE_RW	(_AC(1, UL)<<_PAGE_BIT_RW)
> -#define _PAGE_USER	(_AC(1, UL)<<_PAGE_BIT_USER)
> -#define _PAGE_PWT	(_AC(1, UL)<<_PAGE_BIT_PWT)
> -#define _PAGE_PCD	((_AC(1, UL)<<_PAGE_BIT_PCD) | _PAGE_PWT)
>   

BTW, I just noticed that _PAGE_PWT has been folded into _PAGE_PCD.  This 
seems like a really bad idea to me, since it breaks the rule that 
_PAGE_X == 1 << _PAGE_BIT_X.  I can't think of a specific place where 
this would cause problems, but this kind of non-uniformity always ends 
up biting someone in the arse.

I think having a specific _PAGE_NOCACHE which combines these bits is a 
better approach.

    J

  reply	other threads:[~2008-01-15 17:17 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20080114094814.GA28300@basil.nowhere.org>
2008-01-14 12:56 ` unify pagetable accessors patch causes double fault II Andi Kleen
2008-01-14 13:06   ` Ingo Molnar
2008-01-14 13:58     ` Andi Kleen
2008-01-14 16:44       ` Jeremy Fitzhardinge
2008-01-14 16:56         ` Ingo Molnar
2008-01-14 17:08           ` Andi Kleen
2008-01-14 17:18             ` unify pagetable accessors patch causes double fault III Andi Kleen
2008-01-14 19:00               ` Ingo Molnar
2008-01-14 19:54                 ` Jeremy Fitzhardinge
2008-01-14 20:15                 ` Andi Kleen
2008-01-14 19:52           ` unify pagetable accessors patch causes double fault II Jeremy Fitzhardinge
2008-01-14 22:03       ` Jeremy Fitzhardinge
2008-01-14 22:23         ` Andi Kleen
2008-01-14 22:46           ` Jeremy Fitzhardinge
2008-01-15  1:05             ` Andi Kleen
2008-01-15  1:32               ` Jeremy Fitzhardinge
2008-01-15  1:38                 ` Andi Kleen
2008-01-15 21:03                   ` [patch] x86: lfence fix Ingo Molnar
2008-01-16  0:44                     ` Andi Kleen
2008-01-15 12:55               ` unify pagetable accessors patch causes double fault II Ingo Molnar
2008-01-15 16:53                 ` Andi Kleen
2008-01-15 13:53             ` Ingo Molnar
2008-01-15 17:16               ` Jeremy Fitzhardinge [this message]
2008-01-15 17:23                 ` Folding _PAGE_PWT into _PAGE_PCD (was Re: unify pagetable accessors patch causes double fault II) Andi Kleen
2008-01-15 17:32                   ` Jeremy Fitzhardinge
2008-01-15 17:39                     ` Andi Kleen
2008-01-15 20:30                 ` Venki Pallipadi
2008-01-15 20:45                   ` Jeremy Fitzhardinge
2008-01-15 17:36               ` unify pagetable accessors patch causes double fault II Andi Kleen
2008-01-15 19:43                 ` Jeremy Fitzhardinge

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