Re: + x86-fix-handling-of-the-reservetop-boot-option.patch added to -mm tree

[Yinghai <yinghai.lu@oracle.com>]

On 04/07/2010 03:00 PM, akpm@linux-foundation.org wrote:
> The patch titled
>      x86: fix handling of the 'reservetop' boot option
> has been added to the -mm tree.  Its filename is
>      x86-fix-handling-of-the-reservetop-boot-option.patch
> 
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> 
> See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
> out what to do about this
> 
> The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
> 
> ------------------------------------------------------
> Subject: x86: fix handling of the 'reservetop' boot option
> From: Liang Li <liang.li@windriver.com>
> 
> When specifying the 'reservetop=0xbadc0de' kernel parameter, the kernel
> will stop booting due to a early_ioremap bug that relate to commit
> 8827247ff ("x86: don't define __this_fixmap_does_not_exist()").
> 
> The root cause of boot failure problem is the value of 'slot_virt[i]' was
> initialized in setup_arch->early_ioremap_init.  But later in setup_arch,
> the function 'parse_early_param' will modify 'FIXADDR_TOP' when
> 'reservetop=0xbadc0de' being specified.
> 
> The simplest fix might be use __fix_to_virt(idx0) to get updated value
> of 'FIXADDR_TOP' in '__early_ioremap' instead of reference old value
> from slot_virt[slot] directly.
> 
> Signed-off-by: Liang Li <liang.li@windriver.com>
> Cc: Wang Chen <wangchen@cn.fujitsu.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Yinghai Lu <yinghai@kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
>  arch/x86/mm/ioremap.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff -puN arch/x86/mm/ioremap.c~x86-fix-handling-of-the-reservetop-boot-option arch/x86/mm/ioremap.c
> --- a/arch/x86/mm/ioremap.c~x86-fix-handling-of-the-reservetop-boot-option
> +++ a/arch/x86/mm/ioremap.c
> @@ -537,9 +537,9 @@ __early_ioremap(resource_size_t phys_add
>  		--nrpages;
>  	}
>  	if (early_ioremap_debug)
> -		printk(KERN_CONT "%08lx + %08lx\n", offset, slot_virt[slot]);
> +		printk(KERN_CONT "%08lx + %08lx\n", offset, __fix_to_virt(idx0));
>  
> -	prev_map[slot] = (void __iomem *)(offset + slot_virt[slot]);
> +	prev_map[slot] = (void __iomem *)(offset + __fix_to_virt(idx0));
>  	return prev_map[slot];
>  }
>  
> _

not that simple. but it looks like correct direction.

please consider:
when early_parsing reserve_top, double check if there is left over in prev_map[], and 
reinitialize slot_virt[] and clear old PMD and  setup new PMD if needed.

Thanks

Yinghai