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

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Message-ID: <4D4ADFAD.7060507@zytor.com>
Date:	Thu, 03 Feb 2011 09:02:37 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
CC:	"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>,
	Jeremy Fitzhardinge <Jeremy.Fitzhardinge@...rix.com>,
	Jan Beulich <JBeulich@...ell.com>
Subject: Re: [PATCH] x86/mm/init: respect memblock reserved regions when destroying
 mappings

On 02/03/2011 03:25 AM, Stefano Stabellini wrote:
>>
>> How on Earth would you end up with a reserved region *inside the BRK*?
> 
> I think in practice you cannot, but you can have reserved regions at
> _end, that is the main problem I am trying to solve.
> If we have a reserved region at _end and _end is not PMD aligned, then
> we have a problem.
> 
> I thought that checking for reserved regions before destroying the
> mapping would be a decent solution (because it wouldn't affect the
> normal case); so I ended up checking between _brk_end and _end too.
> 
> Other alternative solutions I thought about but that I discarded because
> they also affect the normal case are:
> 
> - never destroy mappings that could go over _end;
> - always PMD align _end.
> 
> If none of the above are acceptable, I welcome other suggestions :-)
> 

Sounds like the code does the right thing, but the description needs to
be improved.

	-hpa


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

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