linux-kernel - Re: [PATCHv8 00/12] Contiguous Memory Allocator

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Message-ID: <87k4j0ehdl.fsf@erwin.mina86.com>
Date:	Thu, 23 Dec 2010 14:41:26 +0100
From:	Michal Nazarewicz <mina86@...a86.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Kyungmin Park <kmpark@...radead.org>,
	linux-arm-kernel@...ts.infradead.org,
	Daniel Walker <dwalker@...eaurora.org>,
	Johan MOSSBERG <johan.xx.mossberg@...ricsson.com>,
	Mel Gorman <mel@....ul.ie>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Ankita Garg <ankita@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-media@...r.kernel.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCHv8 00/12] Contiguous Memory Allocator

Russell King - ARM Linux <linux@....linux.org.uk> writes:
> Has anyone addressed my issue with it that this is wide-open for
> abuse by allocating large chunks of memory, and then remapping
> them in some way with different attributes, thereby violating the
> ARM architecture specification?
>
> In other words, do we _actually_ have a use for this which doesn't
> involve doing something like allocating 32MB of memory from it,
> remapping it so that it's DMA coherent, and then performing DMA
> on the resulting buffer?

Huge pages.

Also, don't treat it as coherent memory and just flush/clear/invalidate
cache before and after each DMA transaction.  I never understood what's
wrong with that approach.

-- 
Best regards,                                         _     _
 .o. | Liege of Serenly Enlightened Majesty of      o' \,=./ `o
 ..o | Computer Science,  Michal "mina86" Nazarewicz   (o o)
 ooo +--<mina86-tlen.pl>--<jid:mina86-jabber.org>--ooO--(_)--Ooo--
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