Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752875AbXLKQa3 (ORCPT ); Tue, 11 Dec 2007 11:30:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751135AbXLKQaV (ORCPT ); Tue, 11 Dec 2007 11:30:21 -0500 Received: from one.firstfloor.org ([213.235.205.2]:34197 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750865AbXLKQaU (ORCPT ); Tue, 11 Dec 2007 11:30:20 -0500 Date: Tue, 11 Dec 2007 17:30:17 +0100 From: Andi Kleen To: "linux-os (Dick Johnson)" Cc: David Newall , Rene Herman , Paul Rolland , "H. Peter Anvin" , Krzysztof Halasa , Pavel Machek , Andi Kleen , Alan Cox , "David P. Reed" , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , rol@witbe.net Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops Message-ID: <20071211163017.GD16750@one.firstfloor.org> References: <475DE37F.20706@davidnewall.com> <475DE6F4.80702@zytor.com> <475DEB23.1000304@davidnewall.com> <20071211084059.3d03e11d@tux.DEF.witbe.net> <475E5D4B.8020101@keyaccess.nl> <475E7DC2.4060509@davidnewall.com> <475E8D91.20201@keyaccess.nl> <475E95A3.3070801@davidnewall.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1451 Lines: 38 > Most, probably most-all, of the delays to port operations > on modern ix86 machines are not needed at all. Certainly We know this. The problem is that there is no good known way to figure out which machines need it. Also it is typically slow hardware anyways -- the most time critical is probably the 8259, but nobody who cares about performance still uses it except as a fail safe fallback and for those it is better to be conservative. > machines that use bridges to expand port I/O to the ISA > bus do need any such delays. There are exactly two (and It has been observed to be required talking to some older PCI based northbridges too. > (2) I/O operations that have two ports, one an index > port and the other a data port, like the CMOS RTC. Once and PIT etc. Anyways it looks like the discussion here is going in a a loop. I had hoped David would post his test results with another port so that we know for sure that the bus aborts (and not port 80) is the problem on his box. But it looks like he doesn't want to do this. Still removing the bus aborts is probably the correct way to go forward. Only needs a patch now. If nobody beats me to it i'll add one later to my tree. -Andi -- 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/