linux-kernel - Re: [PATCH] kernel parameter vmalloc size fix

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Date:	Fri, 27 Jun 2008 09:55:33 +0800
From:	"Dave Young" <hidave.darkstar@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org, hpa@...or.com,
	"the arch/x86 maintainers" <x86@...nel.org>,
	"Yinghai Lu" <yhlu.kernel@...il.com>
Subject: Re: [PATCH] kernel parameter vmalloc size fix

On Thu, Jun 26, 2008 at 8:14 PM, Ingo Molnar <mingo@...e.hu> wrote:
>
> * Dave Young <hidave.darkstar@...il.com> wrote:
>
>> I do some test about this last weekend, there's some questions, could
>> you help to fix it?
>>
>> 1. MAXMEM :
>>  (-__PAGE_OFFSET - __VMALLOC_RESERVE).
>> The space after VMALLOC_END is included as well, seting it to
>> (VMALLOC_END - PAGE_OFFSET - __VMALLOC_RESERVE), is it right?
>>
>> 2. VMALLOC_OFFSET is not considered in __VMALLOC_RESERVE
>> Should fixed by adding VMALLOC_OFFSET to it.
>>
>> 3. VMALLOC_START :
>>  (((unsigned long)high_memory + 2 * VMALLOC_OFFSET - 1) & ~(VMALLOC_OFFSET - 1))
>> So it's not always 8M, bigger than 8M possible.
>> Set it to ((unsigned long)high_memory + VMALLOC_OFFSET), is it right?
>>
>> Attached the proposed patch. please give some advice.
>
> i've ported it to tip/master, see the patch below. Yinghai, what do you
> think about this change?

Thanks. If there's no objections please add my signed-off line

Signed-off-by: Dave Young <hidave.darkstar@...il.com>

>
>        Ingo
>
> ---
>  arch/x86/mm/pgtable_32.c     |    3 ++-
>  include/asm-x86/page_32.h    |    1 -
>  include/asm-x86/pgtable_32.h |    5 +++--
>  3 files changed, 5 insertions(+), 4 deletions(-)
>
> Index: tip/arch/x86/mm/pgtable_32.c
> ===================================================================
> --- tip.orig/arch/x86/mm/pgtable_32.c
> +++ tip/arch/x86/mm/pgtable_32.c
> @@ -171,7 +171,8 @@ static int __init parse_vmalloc(char *ar
>        if (!arg)
>                return -EINVAL;
>
> -       __VMALLOC_RESERVE = memparse(arg, &arg);
> +       /* Add VMALLOC_OFFSET to the parsed value due to vm area guard hole*/
> +       __VMALLOC_RESERVE = memparse(arg, &arg) + VMALLOC_OFFSET;
>        return 0;
>  }
>  early_param("vmalloc", parse_vmalloc);
> Index: tip/include/asm-x86/page_32.h
> ===================================================================
> --- tip.orig/include/asm-x86/page_32.h
> +++ tip/include/asm-x86/page_32.h
> @@ -95,7 +95,6 @@ extern unsigned int __VMALLOC_RESERVE;
>  extern int sysctl_legacy_va_layout;
>
>  #define VMALLOC_RESERVE                ((unsigned long)__VMALLOC_RESERVE)
> -#define MAXMEM                 (-__PAGE_OFFSET - __VMALLOC_RESERVE)
>
>  extern void find_low_pfn_range(void);
>  extern unsigned long init_memory_mapping(unsigned long start,
> Index: tip/include/asm-x86/pgtable_32.h
> ===================================================================
> --- tip.orig/include/asm-x86/pgtable_32.h
> +++ tip/include/asm-x86/pgtable_32.h
> @@ -56,8 +56,7 @@ void paging_init(void);
>  * area for the same reason. ;)
>  */
>  #define VMALLOC_OFFSET (8 * 1024 * 1024)
> -#define VMALLOC_START  (((unsigned long)high_memory + 2 * VMALLOC_OFFSET - 1) \
> -                        & ~(VMALLOC_OFFSET - 1))
> +#define VMALLOC_START  ((unsigned long)high_memory + VMALLOC_OFFSET)
>  #ifdef CONFIG_X86_PAE
>  #define LAST_PKMAP 512
>  #else
> @@ -73,6 +72,8 @@ void paging_init(void);
>  # define VMALLOC_END   (FIXADDR_START - 2 * PAGE_SIZE)
>  #endif
>
> +#define MAXMEM (VMALLOC_END - PAGE_OFFSET - __VMALLOC_RESERVE)
> +
>  /*
>  * Define this if things work differently on an i386 and an i486:
>  * it will (on an i486) warn about kernel memory accesses that are
>
>



-- 
Regards
dave
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