linux-kernel - Re: [PATCH 2/4] x86: ioremap: fix physical address check

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Date:	Mon, 14 Jun 2010 09:18:23 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, jbarnes@...tuousgeek.org
Subject: Re: [PATCH 2/4] x86: ioremap: fix physical address check

On Fri, 11 Jun 2010 10:43:27 -0700
"H. Peter Anvin" <hpa@...or.com> wrote:

> On 06/11/2010 02:20 AM, Kenji Kaneshige wrote:
> > If the physical address is too high to be handled by ioremap() in
> > x86_32 PAE (e.g. more than 36-bit physical address), ioremap() must
> > return error (NULL). However, current x86 ioremap try to map this too
> > high physical address, and it causes unexpected behavior.
> 
> What unexpected behavior?  It is perfectly legitimately to map such a
> high address in PAE mode.  We have a 36-bit kernel-imposed limit on
> *RAM* in 32-bit mode (because we can't manage more than that), but there
> is no reason it should apply to I/O.
> 

I'm sorry for lack of study. 
How to access it via mapped area by ioremap() ?

Thanks,
-Kame

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