linux-kernel - Re: [PATCH] i386: reduce boot fixmap space

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Message-ID: <4880AD2D.3050407@goop.org>
Date:	Fri, 18 Jul 2008 07:48:13 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Jan Beulich <jbeulich@...ell.com>
CC:	mingo@...e.hu, tglx@...utronix.de, hpa@...or.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i386: reduce boot fixmap space

Jan Beulich wrote:
> As 256 entries are needed, aligning to a 256-entry boundary is
> sufficient and still guarantees the single pte table requirement.
>   

I unified 32 and 64-bit early_ioremap by making 64-bit use the 32-bit 
early_ioremap.  In the process I put a similar entry in fixmap_64.h.  
Would you mind looking to see if the same change is relevant there?

Thanks,
    J

> Signed-off-by: Jan Beulich <jbeulich@...ell.com>
>
> ---
>  include/asm-x86/fixmap_32.h |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> --- linux-2.6.26/include/asm-x86/fixmap_32.h	2008-07-13 23:51:29.000000000 +0200
> +++ 2.6.26-i386-btmap-fixmaps/include/asm-x86/fixmap_32.h	2008-07-18 13:51:16.000000000 +0200
> @@ -94,13 +94,13 @@ enum fixed_addresses {
>  	 * 256 temporary boot-time mappings, used by early_ioremap(),
>  	 * before ioremap() is functional.
>  	 *
> -	 * We round it up to the next 512 pages boundary so that we
> +	 * We round it up to the next 256 pages boundary so that we
>  	 * can have a single pgd entry and a single pte table:
>  	 */
>  #define NR_FIX_BTMAPS		64
>  #define FIX_BTMAPS_NESTING	4
> -	FIX_BTMAP_END = __end_of_permanent_fixed_addresses + 512 -
> -			(__end_of_permanent_fixed_addresses & 511),
> +	FIX_BTMAP_END = __end_of_permanent_fixed_addresses + 256 -
> +			(__end_of_permanent_fixed_addresses & 255),
>  	FIX_BTMAP_BEGIN = FIX_BTMAP_END + NR_FIX_BTMAPS*FIX_BTMAPS_NESTING - 1,
>  	FIX_WP_TEST,
>  #ifdef CONFIG_PROVIDE_OHCI1394_DMA_INIT
>
>
>
> --
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