linux-kernel - Re: [PATCH] x86/mm/init: respect memblock reserved regions when destroying mappings

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Message-ID: <4D54844B.4010007@zytor.com>
Date:	Thu, 10 Feb 2011 16:35:23 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"x86@...nel.org" <x86@...nel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Jan Beulich <JBeulich@...ell.com>
Subject: Re: [PATCH] x86/mm/init: respect memblock reserved regions when destroying
 mappings

On 02/10/2011 03:57 PM, Yinghai Lu wrote:
> On 02/10/2011 03:48 PM, Jeremy Fitzhardinge wrote:
>> On 02/08/2011 11:34 AM, H. Peter Anvin wrote:
>>> On 02/07/2011 07:12 PM, Yinghai Lu wrote:
>>>> why punishing native path with those checking?
>>>>
>>> What happens if you end up with a reserved range in an unfortunate place
>>> on real hardware?
>>
>> Yes, exactly.  The reserved region code isn't very useful if you can't
>> rely on it to reserve stuff.
> 
> assume context is under:
> moving cleanup_highmap() down after brk is concluded, and check memblock_reserved there.
> 
> one case for that: native path, bootloader could put initrd under 512M. and it is with memblock reserved.
> if we check those range with memblock_reserved, initial kernel mapping will not be cleaned up.
> 
> or worse if we are checking if there is any range from __pa(_brk_end) to 512M is with memblock reserved to decide
> if we need to clean-up highmap. it will skip for whole range.
> 

I'm afraid I simply can't parse the above.

	-hpa

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