Message-ID: <47783678.9070706@zytor.com>
Date: Sun, 30 Dec 2007 16:23:20 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: "David P. Reed" <dpreed@reed.com>
CC: Alan Cox <alan@lxorguk.ukuu.org.uk>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Rene Herman <rene.herman@keyaccess.nl>, Ingo Molnar <mingo@elte.hu>,
       Islam Amer <pharon@gmail.com>, Pavel Machek <pavel@ucw.cz>,
       Ingo Molnar <mingo@redhat.com>, Andi Kleen <andi@firstfloor.org>,
       Thomas Gleixner <tglx@linutronix.de>,
       Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override
References: <477711DC.5030800@keyaccess.nl>	<alpine.LFD.1.00.0712300124440.32517@woody.linux-foundation.org>	<20071230144700.78f4605c@the-village.bc.nu>	<20071230152835.GX16946@elte.hu>	<20071230153818.1a554a7e@the-village.bc.nu>	<20071230160132.GA14311@elte.hu>	<20071230164828.039916c8@the-village.bc.nu>	<4777E010.7030703@keyaccess.nl>	<20071230183927.5a5a3c42@the-village.bc.nu>	<4777F297.9070207@keyaccess.nl>	<alpine.LFD.1.00.0712301158410.32517@woody.linux-foundation.org>	<47780B93.4050606@reed.com> <20071230213623.410d480a@the-village.bc.nu> <4778266B.2060502@reed.com>
In-Reply-To: <4778266B.2060502@reed.com>
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David P. Reed wrote:
> Alan Cox wrote:
>>> Now what's interesting is that the outb to port 80 is *faster* than 
>>> an outb to an unused port, on my machine.  So there's something there 
>>> - actually accepting the bus transaction.   In the ancient 5150 PC, 
>>> 80 was     
>>
>> Yes and I even told you a while back how to verify where it is. From the
>> timing you get its not on the LPC bus but chipset core so pretty
>> certainly an SMM trap as other systems with the same chipset don't have
>> the bug. Probably all that is needed is a BIOS upgrade
>>
>>   
> Actually, I could see whether it was SMM trapping due to AMD MSR's that 
> would allow such trapping, performance or debug registers.  Nothing was 
> set to trap with SMI or other traps on any port outputs.   But I'm 
> continuing to investigate for a cause.  It would be nice if it were a 
> BIOS-fixable problem.  It would be even nicer if the BIOS were GPL...

If it was an SMM trap, I would expect it to be trapped in the SuperIO chip.

	-hpa
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