linux-kernel - Re: How to alloc highmem page below 4GB on i386?

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Message-ID: <20080704195800.4ef6e00a@mjolnir.drzeus.cx>
Date:	Fri, 4 Jul 2008 19:58:00 +0200
From:	Pierre Ossman <drzeus-list@...eus.cx>
To:	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: How to alloc highmem page below 4GB on i386?

On Mon, 30 Jun 2008 20:03:23 +0200
Pierre Ossman <drzeus-list@...eus.cx> wrote:

> Simple question. How do I allocate a page from highmem, that's still
> within 32 bits? x86_64 has the DMA32 zone, but i386 has just HIGHMEM.
> As most devices can't DMA above 32 bit, I have 3 GB of memory that's
> not getting decent usage (or results in needless bouncing). What to do?
> 
> I tried just enabling CONFIG_DMA32 for i386, but there is some guard
> against too many memory zones. I'm assuming this is there for a good
> reason?
> 

Anyone?

-- 
     -- Pierre Ossman

  Linux kernel, MMC maintainer        http://www.kernel.org
  rdesktop, core developer          http://www.rdesktop.org

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