linux-kernel - Re: [PATCH 1 of 8] x86: page.h: unify constants

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Date:	Mon, 7 Jan 2008 18:17:12 +0100
From:	Andi Kleen <ak@...e.de>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...e.de>,
	Glauber de Oliveira Costa <glommer@...il.com>,
	Jan Beulich <jbeulich@...ell.com>
Subject: Re: [PATCH 1 of 8] x86: page.h: unify constants


> +
> +#define LARGE_PAGE_SIZE		(_AC(1,UL) << PMD_SHIFT)
> +#define LARGE_PAGE_MASK		(~(LARGE_PAGE_SIZE-1))
> +
> +#define HPAGE_SHIFT		PMD_SHIFT
> +#define HPAGE_SIZE		(_AC(1,UL) << HPAGE_SHIFT)
> +#define HPAGE_MASK		(~(HPAGE_SIZE - 1))
> +#define HUGETLB_PAGE_ORDER	(HPAGE_SHIFT - PAGE_SHIFT)

This will actually stop being the same soon with GB pages which
are only supported on 64bit.

> +
> +#ifdef CONFIG_X86_64
> +#define THREAD_ORDER	1
> +#define THREAD_SIZE  (PAGE_SIZE << THREAD_ORDER)
> +#define CURRENT_MASK (~(THREAD_SIZE-1))
> +
> +#define EXCEPTION_STACK_ORDER 0
> +#define EXCEPTION_STKSZ (PAGE_SIZE << EXCEPTION_STACK_ORDER)
> +
> +#define DEBUG_STACK_ORDER (EXCEPTION_STACK_ORDER + 1)
> +#define DEBUG_STKSZ (PAGE_SIZE << DEBUG_STACK_ORDER)
> +
> +#define IRQSTACK_ORDER 2
> +#define IRQSTACKSIZE (PAGE_SIZE << IRQSTACK_ORDER)

This all seems hardly 64bit specific (except for THREAD_ORDER
but you can probably handle that in Kconfig or just get rid
of it for 32bit)

> +#define __PHYSICAL_START	CONFIG_PHYSICAL_START

Also not 64bit specific

> +#ifdef CONFIG_X86_PAE
> +#define __PHYSICAL_MASK_SHIFT	36

I originally added the PHYSICAL_MASK stuff to deal with masking off NX,
but I must admit it wasn't the best idea I ever had. It would be probably
better to just get rid of it and always mask off the high reserved flags bit
explicitely. If you make that 0 then there should be no special
case for PAE.

-Andi
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