From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757559Ab0I1RTv (ORCPT ); Tue, 28 Sep 2010 13:19:51 -0400 Received: from smtp.ctxuk.citrix.com ([62.200.22.115]:59366 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757165Ab0I1RTu (ORCPT ); Tue, 28 Sep 2010 13:19:50 -0400 X-IronPort-AV: E=Sophos;i="4.57,248,1283731200"; d="scan'208";a="2081497" Date: Tue, 28 Sep 2010 18:19:37 +0100 From: Stefano Stabellini X-X-Sender: sstabellini@kaball-desktop To: Jeremy Fitzhardinge CC: Stefano Stabellini , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , "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 In-Reply-To: <4CA2223B.9040400@goop.org> Message-ID: References: <1285676218-26218-12-git-send-email-stefano.stabellini@eu.citrix.com> <20100928123925.GA18208@elte.hu> <4CA2223B.9040400@goop.org> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 28 Sep 2010, Jeremy Fitzhardinge wrote: > On 09/28/2010 07:00 AM, Stefano Stabellini wrote: > > On Tue, 28 Sep 2010, Ingo Molnar wrote: > >> * stefano.stabellini@eu.citrix.com wrote: > >> > >>> From: Stephen Tweedie > >>> > >>> Add a Xen mtrr type, and reorganise mtrr initialisation slightly to > >>> allow the mtrr driver to set up num_var_ranges (Xen needs to do this by > >>> querying the hypervisor itself.) > >>> > >>> [ Impact: add basic MTRR support ] > >>> > >>> Signed-off-by: Stephen Tweedie > >>> Signed-off-by: Jeremy Fitzhardinge > >>> Signed-off-by: Stefano Stabellini > >>> --- > >>> arch/x86/kernel/cpu/mtrr/Makefile | 2 +- > >>> arch/x86/kernel/cpu/mtrr/main.c | 3 + > >>> arch/x86/kernel/cpu/mtrr/mtrr.h | 7 ++ > >>> arch/x86/kernel/cpu/mtrr/xen.c | 110 +++++++++++++++++++++++++++++++++++++ > >>> 4 files changed, 121 insertions(+), 1 deletions(-) > >>> create mode 100644 arch/x86/kernel/cpu/mtrr/xen.c > >> Still NAK, for the very same reasons as we NAK-ed it the previous time: > >> /proc/mtrr is a problematic and complicated legacy interface that should > >> die. Any modern X server will do the right thing via PAT. > >> > > Sorry I should have read the original thread more carefully: I didn't > > realize this patch had been NAK-ed. > > > > However it is not a problem because we can easily disable MTRRs from Xen > > and with no cpu_has_mtrr the kernel would still boot fine on Xen. > > Also I think we do have PAT support nowadays but I'll let Jeremy comment > > on that. > > 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. Yeah, I have already tested a prototype patch to xen to mask the MTRR cpu features and everything seems to run fine on my testbox.