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

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Message-ID: <4C1275BF.3070605@zytor.com>
Date:	Fri, 11 Jun 2010 10:43:27 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
CC:	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 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.

	-hpa
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