linux-kernel - Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc.

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Date:	Sun, 16 Dec 2007 15:34:58 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Pavel Machek <pavel@....cz>
CC:	"David P. Reed" <dpreed@...d.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Rene Herman <rene.herman@...access.nl>
Subject: Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80
 on some AMD64x2 laptops, etc.

Pavel Machek wrote:
> Hi!
> 
>> The process of safely making delicate changes here is beyond my 
>> responsibility as just a user - believe me, I'm not suggesting that a risky 
>> fix be put in .24.   I can patch my own kernels, and I can even share an 
>> unofficial patch with others for now, or suggest that Fedora and Ubuntu add 
>> it to their downstream.
>>
>> May I make a small suggestion, though.   If the decision is a DMI-keyed 
>> switch from out-80 to udelay(2)  gets put in, perhaps there should also be 
>> a way for people to test their own configuration for the underlying problem 
>> made available as a script.   Though it is a "hack", all you need to freeze 
>> a problem system is to run a loop doing about 1000 "cat /dev/nvram > 
>> /dev/null"  commands.  If that leads to a freeze, one might ask to have the 
>> motherboard added to the DMI-key list.
> 
> Can you freeze it by catting /dev/rtc, too? That may be significant,
> because that is readable for group audio (at least on some
> systems)... which would smell like "small security hole" to me.
> 									Pavel

Heck, on my system (Fedora 7), it's mode 644...

	-hpa
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