linux-kernel - Re: [PATCH 06/20] early_res: seperate common memmap func from e820.c to fw

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Date:	Mon, 22 Mar 2010 15:25:54 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Ingo Molnar <mingo@...e.hu>, David Miller <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	benh@...nel.crashing.org, hpa@...or.com, jbarnes@...tuousgeek.org,
	ebiederm@...ssion.com, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH 06/20] early_res: seperate common memmap func from e820.c
 to fw_memmap.cy

On 03/22/2010 03:09 PM, Thomas Gleixner wrote:
> Yinghai,
> 
> On Mon, 22 Mar 2010, Yinghai Lu wrote:
>> On 03/22/2010 12:37 PM, Ingo Molnar wrote:
>>> * Thomas Gleixner <tglx@...utronix.de> wrote:
>>
>>>> The main point is that there is still no answer why lmb cannot be used and 
>>>> the reposted patch still is a full move of the x86 e820 functions into 
>>>> kernel/fw_memmap.c.
>>>>
>>>> That's not a generalization, that's simply a relocation of x86 code to 
>>>> kernel/. And I agree with Dave and Ben that this is an useless exercise.
>>>
>>> ok - i think you are right. Yinghai, mind having a look at using
>>> lib/lmb.c for all this?
>>
>> 1. need to keep e820
> 
>   That's neither an argument for using lmb nor an argument not to use
>   lmb. e820 is x86 specific BIOS wreckage and it's whole purpose is
>   just to feed information into a (hopefully) generic early resource
>   management facility.
> 
>   e820 _CANNOT_ be generalized. Period.
> 
>> 2. use e820 range with RAM to fill lmb.memory when finizing_e820
> 
>   What's finizing_e820 ???
 finish_e820_parsing();
> 
>> 3. use lmb.reserved to replace early_res.
> 
>   What's the implication of doing that ?

early_res array is only corresponding to lmb.reserved, aka reserved region from kernel.

>  
>> current lmb is merging the region, we can not use name tag any more.
> 
>   What's wrong with merging of regions ? Are you arguing about a
>   specific region ("the region") ?

> 
>   Which name tag ? And why is that name tag important ?

struct early_res {
        u64 start, end;
        char name[15];
        char overlap_ok;
};

>  
>> may need to dump early_memtest, and use early_res for bootmem at
>> first.
> 
>   Why exactly might early_memtest not longer be possible ?
early_memtest need to call find_e820_area_size
current lmb doesn't have that kind of find util.
the one memory subtract reserved memory by kernel.
> 
>   What means "early_res for bootmem" ?

use early_res to replace bootmem, the CONFIG_NO_BOOTMEM.
that need early_res can be double or increase the slots automatically.

Yinghai
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