linux-kernel - Re: {PATCH] x86: print out initial max_pfn

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Date:	Mon, 16 Mar 2009 19:36:17 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: {PATCH] x86: print out initial max_pfn_mapped

Yinghai Lu wrote:
> Impact: more debug info
> 
> check range that is mapped before init_memory_mapping().
> also make 64bit have max_pfn_mapped assigned before that calling
> 
> Index: linux-2.6/arch/x86/mm/init.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/mm/init.c
> +++ linux-2.6/arch/x86/mm/init.c
> @@ -65,12 +65,11 @@ static void __init find_early_table_spac
>  	 */
>  #ifdef CONFIG_X86_32
>  	start = 0x7000;
> -	e820_table_start = find_e820_area(start, max_pfn_mapped<<PAGE_SHIFT,
> -					tables, PAGE_SIZE);
> -#else /* CONFIG_X86_64 */
> +#else
>  	start = 0x8000;
> -	e820_table_start = find_e820_area(start, end, tables, PAGE_SIZE);
>  #endif
> +	e820_table_start = find_e820_area(start, max_pfn_mapped<<PAGE_SHIFT,
> +					tables, PAGE_SIZE);
>  	if (e820_table_start == -1UL)
>  		panic("Cannot find space for the kernel page tables");
>  

This doesn't seem to match anything anywhere in the description.
Furthermore, why do we even have a different starting address for
different architectures?  If anything, this starting address is way too
low (hogging ZONE_DMA and all that...)

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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