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

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Message-ID: <4D4A3782.3050702@zytor.com>
Date:	Wed, 02 Feb 2011 21:05:06 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
CC:	linux-kernel@...r.kernel.org, tglx@...utronix.de, 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 01/31/2011 07:18 AM, Stefano Stabellini wrote:
> x86/mm/init: respect memblock reserved regions when destroying mappings
> 
> In init_memory_mapping we are destroying all the mappings between
> _brk_end and _end, no matter if some memory areas in that range have
> been reserved using memblock_x86_reserve_range.
> Besides if _end is not pmd aligned we might destroy the
> mappings for valid memory between _end and the following pmd.
> 
> In order to avoid this problem, before clearing any pmds we check if the
> corresponding memory area has been reserved and we only destroy the
> mapping if it hasn't.
> 
> We found this problem because under Xen we have a valid mapping at _end,
> and if _end is not pmd aligned the current code destroys the initial
> part of it.
> 
> In practice this fix does not have any impact on native.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>

How on Earth would you end up with a reserved region *inside the BRK*?

	-hpa

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

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