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Date: Fri, 25 Apr 2008 17:06:12 -0700
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Linus Torvalds <torvalds@linux-foundation.org>
CC: Ingo Molnar <mingo@elte.hu>, linux-kernel@vger.kernel.org,
       Andrew Morton <akpm@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [git pull] x86 PAT changes
References: <20080424225625.GB8717@elte.hu> <alpine.LFD.1.10.0804251351511.2779@woody.linux-foundation.org>
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Linus Torvalds wrote:
> 
> So why is PAT dependent on NONPROMISC_DEVMEM here?
> 
> It seems pointless and wrong. Somebody might want to have both the full 
> /dev/mem and PAT.
> 

The problem is that that can create cached/uncached aliases, which can 
cause some processors to lock up (especially AMD is known to have a lot 
of errata in this area.)

	-hpa