Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755482AbYAIVsT (ORCPT ); Wed, 9 Jan 2008 16:48:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752020AbYAIVsJ (ORCPT ); Wed, 9 Jan 2008 16:48:09 -0500 Received: from smtp-outbound-1.vmware.com ([65.113.40.141]:41488 "EHLO smtp-outbound-1.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750825AbYAIVsI (ORCPT ); Wed, 9 Jan 2008 16:48:08 -0500 Subject: Re: [linux-kernel] Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override. From: Zachary Amsden To: "H. Peter Anvin" Cc: "David P. Reed" , Avi Kivity , Christer Weinigel , Ondrej Zary , Rene Herman , Bodo Eggert <7eggert@gmx.de>, Ingo Molnar , Alan Cox , Paul Rolland , Pavel Machek , Thomas Gleixner , linux-kernel@vger.kernel.org, Ingo Molnar , rol In-Reply-To: <47845972.9090803@zytor.com> References: <9BdU5-1YW-9@gated-at.bofh.it> <200801081810.58904.linux@rainbow-software.org> <4783B1B2.6070005@reed.com> <200801081838.16241.linux@rainbow-software.org> <4783C4A6.9060402@reed.com> <20080108185120.3ff7ed18@lxorguk.ukuu.org.uk> <4783CBD9.7020709@reed.com> <1199847162.7369.323.camel@bodhitayantram.eng.vmware.com> <47845972.9090803@zytor.com> Content-Type: text/plain Date: Wed, 09 Jan 2008 13:53:34 -0800 Message-Id: <1199915614.7369.367.camel@bodhitayantram.eng.vmware.com> Mime-Version: 1.0 X-Mailer: Evolution 2.10.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1027 Lines: 26 On Tue, 2008-01-08 at 21:19 -0800, H. Peter Anvin wrote: > Zachary Amsden wrote: > > > > BTW, it isn't ever safe to pass port 0x80 through to hardware from a > > virtual machine; some OSes use port 0x80 as a hardware available scratch > > register (I believe Darwin/x86 did/does this during boot). > > That's funny, because there is definitely no guarantee that you get back > what you read (well, perhaps there is on Apple.) According to Phoenix Technologies book "System BIOS for IBM PCs, Compatibles and EISA Computers, 2nd Edition", the I/O port list gives port 0080h R/W Extra page register (temporary storage) Despite looking, I've never seen it documented anywhere else, but I believe it works on just about every PC platform. Except, apparently, my laptop. Zach -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/