[PATCH] i386: reduce boot fixmap space

[PATCH] i386: reduce boot fixmap space

[Jan Beulich]

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

Signed-off-by: Jan Beulich <jbeulich@novell.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

Re: [PATCH] i386: reduce boot fixmap space

[Jeremy Fitzhardinge]

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@novell.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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>   

Re: [PATCH] i386: reduce boot fixmap space

[Jan Beulich]

>>> Jeremy Fitzhardinge <jeremy@goop.org> 18.07.08 16:48 >>>
>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?

I'm sure it would be applicable there, too, but checking my just refreshed
x86.git snapshot doesn't show anything like that in fixmap_64.h.

Jan

Re: [PATCH] i386: reduce boot fixmap space

[H. Peter Anvin]

Jan Beulich wrote:
> As 256 entries are needed, aligning to a 256-entry boundary is
> sufficient and still guarantees the single pte table requirement.
> 
> Signed-off-by: Jan Beulich <jbeulich@novell.com>

Manually applied to x86/fixmap, thanks.

	-hpa