linux-kernel - Re: [PATCH] mm,x86: fix span coverage in e820_all

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Date:	Tue, 10 Dec 2013 13:52:16 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Xishi Qiu <qiuxishi@...wei.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Linn Crosetto <linn@...com>, Pekka Enberg <penberg@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux MM <linux-mm@...ck.org>
Subject: Re: [PATCH] mm,x86: fix span coverage in e820_all_mapped()

On Tue, Dec 10, 2013 at 1:29 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 12/10/2013 01:06 PM, Yinghai Lu wrote:
>> On Tue, Dec 10, 2013 at 1:06 AM, Xishi Qiu <qiuxishi@...wei.com> wrote:
>>> In the following case, e820_all_mapped() will return 1.
>>> A < start < B-1 and B < end < C, it means <start, end> spans two regions.
>>> <start, end>:           [start - end]
>>> e820 addr:          ...[A - B-1][B - C]...
>>
>> should be [start, end) right?
>> and
>> [A, B),[B, C)
>>
>
> What happens if it spans more than two regions?

[A, B), [B+1, C), [C+1, D) ?
start in [A, B), and end in [C+1, D).

old code:
first with [A, B), start set to B.
then with [B+1, C), start still keep as B.
then with [C+1, D), start still keep as B.
at last still return 0...aka not_all_mapped.

old code is still right.
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