From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757590Ab0I1STz (ORCPT ); Tue, 28 Sep 2010 14:19:55 -0400 Received: from terminus.zytor.com ([198.137.202.10]:60329 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752612Ab0I1STy (ORCPT ); Tue, 28 Sep 2010 14:19:54 -0400 Message-ID: <4CA231A8.5000100@zytor.com> Date: Tue, 28 Sep 2010 11:19:20 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100907 Fedora/3.1.3-1.fc13 Thunderbird/3.1.3 MIME-Version: 1.0 To: Jeremy Fitzhardinge CC: Stefano Stabellini , Ingo Molnar , Thomas Gleixner , "linux-kernel@vger.kernel.org" , "xen-devel@lists.xensource.com" , Jeremy Fitzhardinge , "sct@redhat.com" Subject: Re: [PATCH 12/12] xen/mtrr: Add mtrr_if support for Xen mtrr References: <1285676218-26218-12-git-send-email-stefano.stabellini@eu.citrix.com> <20100928123925.GA18208@elte.hu> <4CA2223B.9040400@goop.org> <4CA22C3C.3020209@zytor.com> <4CA2302C.3000201@goop.org> In-Reply-To: <4CA2302C.3000201@goop.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/28/2010 11:13 AM, Jeremy Fitzhardinge wrote: > On 09/28/2010 10:56 AM, H. Peter Anvin wrote: >> On 09/28/2010 10:13 AM, Jeremy Fitzhardinge wrote: >>> Yes, we could just mask out the MTRR CPU feature and rely entirely on PAT. >>> >>> The alternative would be to use the wrmsr hooks to emulate the Intel >>> MTRR registers by mapping them to hypercalls, but that seems needlessly >>> complex. >>> >> Indeed. Relying on pure PAT is the Right Thing[TM]. > > Is there a plan to formally deprecate /proc/mtrr and the kernel > infrastructure behind it? > No, and we really can't do it for a couple of reasons: a) Pre-PAT hardware; b) MTRRs and PAT interact on hardware; c) MTRRs, but not PAT, interact with SMM. However, since a virtual machine like Xen doesn't have these issues, it doesn't apply. -hpa