linux-kernel - Re: [PATCH 4/8] x86 boot: allow overlapping ebda and efi memmap memory ranges

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Date:	Sun, 15 Jun 2008 23:54:38 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Paul Jackson" <pj@....com>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Jack Steiner" <steiner@....com>, "Mike Travis" <travis@....com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	"Huang, Ying" <ying.huang@...el.com>,
	"Andi Kleen" <andi@...stfloor.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>
Subject: Re: [PATCH 4/8] x86 boot: allow overlapping ebda and efi memmap memory ranges

On Sun, Jun 15, 2008 at 11:30 PM, Paul Jackson <pj@....com> wrote:
> From: Paul Jackson <pj@....com>
>
> In order to support EFI firmware which places the EFI memmap within
> the EBDA (Extended BIOS Data Area), allow for the possibility that we
> might try to reserve_early() the "EFI memmap" area twice, once as part
> of the larger EBDA area and once by itself.  Since the reserve_early()
> mechanism does not allow such double reservations, detect and avoid the
> "EFI memmap" reserve_early() call if it would overlap the EBDA area.
>
> Signed-off-by: Paul Jackson <pj@....com>
>
> ---
>  arch/x86/kernel/efi.c       |    3 ++-
>  arch/x86/kernel/head.c      |   12 +++++++++++-
>  include/asm-x86/bios_ebda.h |    1 +
>  include/asm-x86/e820.h      |    1 +
>  4 files changed, 15 insertions(+), 2 deletions(-)
>
> --- linux.orig/arch/x86/kernel/efi.c    2008-06-13 00:51:17.350774123 -0700
> +++ linux/arch/x86/kernel/efi.c 2008-06-13 00:53:10.053599898 -0700
> @@ -253,7 +253,8 @@ void __init efi_reserve_early(void)
>                boot_params.efi_info.efi_memdesc_size;
>        memmap.desc_version = boot_params.efi_info.efi_memdesc_version;
>        memmap.desc_size = boot_params.efi_info.efi_memdesc_size;
> -       reserve_early(pmap, pmap + memmap.nr_map * memmap.desc_size,
> +       if (!range_in_ebda_area(pmap, pmap + memmap.nr_map * memmap.desc_size))
> +               reserve_early(pmap, pmap + memmap.nr_map * memmap.desc_size,
>                      "EFI memmap");
>  }
>
> --- linux.orig/arch/x86/kernel/head.c   2008-06-13 00:51:17.350774123 -0700
> +++ linux/arch/x86/kernel/head.c        2008-06-13 00:52:45.208095174 -0700
> @@ -6,6 +6,9 @@
>
>  #define BIOS_LOWMEM_KILOBYTES 0x413
>
> +static unsigned int __initdata ebda_start;
> +static unsigned int __initdata ebda_end;
> +
>  /*
>  * The BIOS places the EBDA/XBDA at the top of conventional
>  * memory, and usually decreases the reported amount of
> @@ -51,7 +54,14 @@ void __init reserve_ebda_region(void)
>                lowmem = 0x9f000;
>
>        /* reserve all memory between lowmem and the 1MB mark */
> -       reserve_early(lowmem, 0x100000, "BIOS reserved");
> +       ebda_start = lowmem;
> +       ebda_end = 0x100000;
> +       reserve_early(ebda_start, ebda_end, "BIOS reserved");
> +}
> +
> +int __init range_in_ebda_area(u64 start, u64 end)
> +{
> +       return start >= ebda_start && end <= ebda_end;
>  }
>
>  void __init reserve_setup_data(void)
> --- linux.orig/include/asm-x86/bios_ebda.h      2008-06-13 00:51:17.350774123 -0700
> +++ linux/include/asm-x86/bios_ebda.h   2008-06-13 00:51:31.819650439 -0700
> @@ -15,5 +15,6 @@ static inline unsigned int get_bios_ebda
>  }
>
>  void reserve_ebda_region(void);
> +int range_in_ebda_area(u64 start, u64 end);
>
>  #endif /* _MACH_BIOS_EBDA_H */
> --- linux.orig/include/asm-x86/e820.h   2008-06-13 00:51:17.354774365 -0700
> +++ linux/include/asm-x86/e820.h        2008-06-13 00:51:31.831651166 -0700
> @@ -84,6 +84,7 @@ extern unsigned long end_user_pfn;
>  extern u64 find_e820_area(u64 start, u64 end, u64 size, u64 align);
>  extern u64 find_e820_area_size(u64 start, u64 *sizep, u64 align);
>  extern void reserve_early(u64 start, u64 end, char *name);
> +extern int range_in_ebda_area(u64 start, u64 end);
>  extern void free_early(u64 start, u64 end);
>  extern void early_res_to_bootmem(u64 start, u64 end);
>  extern int page_is_reserved_early(unsigned long pagenr);

how about patial overlapping?

YH
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