From: "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
To: "David P. Reed" <dpreed-pPKjjScK5eQ@public.gmane.org>
Cc: kvm-devel
<kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>,
Rene Herman <rene.herman-cENuUygGYd//D1n+0JDH9g@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>,
Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Pavel Machek <pavel-+ZI9xUNit7I@public.gmane.org>
Subject: Re: [PATCH] x86_64: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc.
Date: Fri, 14 Dec 2007 18:20:04 -0800 [thread overview]
Message-ID: <476339D4.2090802@zytor.com> (raw)
In-Reply-To: <4763385E.9040106-pPKjjScK5eQ@public.gmane.org>
David P. Reed wrote:
>
> I believe (though no one seems to have confirming documentation from the
> chipset or motherboard vendor) that port 80 is actually functional for
> some unknown function on these machines. (They do respond to "in"
> instructions faster than a bus cycle abort does - more evidence).
>
This is normal. IN from port 0x80 is used by the DMA address map chip.
As far as I understand, there are other laptops with the same chipset
which don't have this problem, so it's likely either a motherboard or
firmware issue. My guess is that they probably let debugging code out
in the field (trap port 0x80 in SMM, and then try to output it on some
debugging bus.)
-hpa
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next prev parent reply other threads:[~2007-12-15 2:20 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <466F0941.9060201@reed.com>
[not found] ` <1181682498.8176.224.camel@chaos>
[not found] ` <469578CD.3080609@reed.com>
[not found] ` <1184216528.12353.203.camel@chaos>
[not found] ` <1184218962.12353.209.camel@chaos>
[not found] ` <46964352.7040301@reed.com>
[not found] ` <1184253339.12353.223.camel@chaos>
[not found] ` <469697C6.50903@reed.com>
[not found] ` <1184274754.12353.254.camel@chaos>
[not found] ` <4761F193.7090400@reed.com>
2007-12-14 16:08 ` [PATCH] x86_64: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc Avi Kivity
2007-12-15 2:13 ` David P. Reed
[not found] ` <4763385E.9040106-pPKjjScK5eQ@public.gmane.org>
2007-12-15 2:20 ` H. Peter Anvin [this message]
2007-12-19 15:03 ` Avi Kivity
2007-12-17 18:14 ` linux-os (Dick Johnson)
[not found] ` <Pine.LNX.4.61.0712171307150.4584-KUYkVxoy1ibZ8u7sGK6rWdBPR1lH4CV8@public.gmane.org>
2007-12-17 18:54 ` Rene Herman
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