linux-kernel - Re: [patch] x86: Fix /dev/mem mmap breakage when PAT is disabled

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Date:	Thu, 30 Oct 2008 13:21:03 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Ravikiran G Thirumalai <kiran@...lex86.org>
Cc:	Ingo Molnar <mingo@...e.hu>, venkatesh.pallipadi@...el.com,
	linux-kernel@...r.kernel.org, tim@...lemp.com, shai@...lex86.org
Subject: Re: [patch] x86: Fix /dev/mem mmap breakage when PAT is disabled

On Wed, 29 Oct 2008 19:02:03 -0700
Ravikiran G Thirumalai <kiran@...lex86.org> wrote:

> Fix mmap to /dev/mem when CONFIG_X86_PAT is off and
> CONFIG_STRICT_DEVMEM is off
> 
> mmap to /dev/mem on kernel memory has been failing since the
> introduction of PAT (CONFIG_STRICT_DEVMEM=n case).   Seems like
> the check to avoid cache aliasing with PAT is kicking in even
> when PAT is disabled. The bug seems to have crept in 2.6.26.
> 
> This patch makes sure that mmap to regular kernel memory
> succeeds if CONFIG_STRICT_DEVMEM=n and
> PAT is disabled.  The checks to avoid cache aliasing
> still happens if PAT is enabled.

well... technically the aliases are bad without PAT as well...


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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