From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752078AbZERI7q (ORCPT ); Mon, 18 May 2009 04:59:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751918AbZERI7f (ORCPT ); Mon, 18 May 2009 04:59:35 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:51304 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751073AbZERI7f (ORCPT ); Mon, 18 May 2009 04:59:35 -0400 Date: Mon, 18 May 2009 10:59:02 +0200 From: Ingo Molnar To: Jeremy Fitzhardinge Cc: "Eric W. Biederman" , Jesse Barnes , the arch/x86 maintainers , Linux Kernel Mailing List , Xen-devel , Linus Torvalds , "H. Peter Anvin" , Thomas Gleixner Subject: Re: [GIT PULL] xen /proc/mtrr implementation Message-ID: <20090518085902.GE10687@elte.hu> References: <1242170864-13560-1-git-send-email-jeremy@goop.org> <20090513133021.GA7277@elte.hu> <4A0ADBA2.2020300@goop.org> <20090515182757.GA19256@elte.hu> <4A0DCC11.10307@goop.org> <4A0DFF78.6000501@goop.org> <20090515202250.0f1218ef@jbarnes-g45> <4A10EAC4.9070701@goop.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A10EAC4.9070701@goop.org> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Jeremy Fitzhardinge wrote: > It's not really virtualized. We're talking about dom0, which is > the guest domain which has access to the real machine's real > hardware; the MTRR is part of that. That is a really broken model and design of virtualization: splitting the hypervisor into Xen and then a separate Linux dom0 entity because reality called home a few years ago and you needed actual working drivers and hardware support and a developer community to pull that off ... Here Xen invades an already fragile piece of upstream code (/proc/mtrr) that is obsolete and on the way out. If you want a solution you should add PAT support to Xen and you should use recent upstream kernels. Or you should emulate /proc/mtrr in _Xen the hypervisor_, if you really care that much - without increasing the amount of crap in Linux. Without a better reason than what you've given so far the answer is really: "no thanks" ... My suspicion is that Linus would (rightfully) refuse to pull such a broken approach from me, so why should i pull it? If i'm wrong and if you can get an Acked-by from Linus _before_ sending a pull request we can override my NAK. I've Cc:-ed him, in case he wants to express an opinion. Ingo