Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757346AbYAICrg (ORCPT ); Tue, 8 Jan 2008 21:47:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756326AbYAICrT (ORCPT ); Tue, 8 Jan 2008 21:47:19 -0500 Received: from smtp-outbound-1.vmware.com ([65.113.40.141]:59828 "EHLO smtp-outbound-1.vmware.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756226AbYAICrS (ORCPT ); Tue, 8 Jan 2008 21:47:18 -0500 Subject: Re: [linux-kernel] Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override. From: Zachary Amsden To: "David P. Reed" , Avi Kivity Cc: Christer Weinigel , Ondrej Zary , "H. Peter Anvin" , 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: <4783CBD9.7020709@reed.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> Content-Type: text/plain Date: Tue, 08 Jan 2008 18:52:42 -0800 Message-Id: <1199847162.7369.323.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: 1745 Lines: 40 On Tue, 2008-01-08 at 14:15 -0500, David P. Reed wrote: > Alan Cox wrote: > > The natsemi docs here say otherwise. I trust them not you. > > > As well you should. I am honestly curious (for my own satisfaction) as > to what the natsemi docs say the delay code should do (can't imagine > they say "use io port 80 because it is unused"). I don't have any What is the outcome of this thread? Are we going to use timing based port delays, or can we finally drop these things entirely on 64-bit architectures? I a have a doubly vested interest in this, both as the owner of an affected HP dv9210us laptop and as a maintainer of paravirt code - and would like 64-bit Linux code to stop using I/O to port 0x80 in both cases (as I suspect would every other person involved with virtualization). 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). This means simultaneous execution of two virtual machines can interleave port 0x80 values or share data with a hardware provided covert channel. This means KVM should be trapping port 0x80 access, which is really expensive, or alternatively, Linux should not be using port 0x80 for timing bus access on modern (64-bit) hardware. I've tried to follow this thread, but with all the jabs, 1-ups, and obscure legacy hardware pageantry going on, it isn't clear what we're really doing. Thanks, 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/