linux-kernel - Re: early_res and find_e820

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Date:	Mon, 03 Mar 2008 20:23:48 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Huang, Ying" <ying.huang@...el.com>
CC:	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>, Andi Kleen <ak@...e.de>,
	linux-kernel@...r.kernel.org
Subject: Re: early_res and find_e820_area for i386?

Huang, Ying wrote:
> Hi,
> 
> Before bootmem allocator is available, kernel needs allocate memory
> pages such as page table and some NUMA structures. On x86_64, this is
> done by early_res and find_e820_area. On i386, this is done through
> using the memory area after kernel itself which is tracked with
> init_pg_tables_end.
> 
> Is it better to implement early_res and find_e820_area on i386? Can we
> trust E820 table on i386?
> 
> Or we add an early_alloc, which allocate memory from the memory area
> after kernel itself and check the early_res areas and E820 table too.
> 
> BTW: Why not merge e820_32.c and e820_64.c? At least part of them.
> 

What we *should* do, on both i386 and x86-64, is to create a synthetic 
e820 table of any non-e820 information, and then yes, we should merge 
the code.

In other words, we should have an e820 table which reflects what the 
kernel considers true about the memory space.

	-hpa
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