From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756920AbbIDAvU (ORCPT ); Thu, 3 Sep 2015 20:51:20 -0400 Received: from g4t3426.houston.hp.com ([15.201.208.54]:44857 "EHLO g4t3426.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752873AbbIDAvS (ORCPT ); Thu, 3 Sep 2015 20:51:18 -0400 Message-ID: <1441327726.3277.109.camel@hpe.com> Subject: Re: Fwd: [PATCH] x86: Use larger chunks in mtrr_cleanup From: Toshi Kani To: "Luis R. Rodriguez" Cc: Prarit Bhargava , Stuart Hayes , tglx@linutronix.de, mingo@redhat.com, "H. Peter Anvin" , linux-kernel@vger.kernel.org, x86@kernel.org, mcgrof@do-not-panic.com, Toshi Kani , Jan Beulich , Juergen Gross Date: Thu, 03 Sep 2015 18:48:46 -0600 In-Reply-To: <20150903235429.GZ8051@wotan.suse.de> References: <20150903175902.GU8051@wotan.suse.de> <55E88D06.3040608@redhat.com> <20150903184029.GV8051@wotan.suse.de> <1441308162.3277.20.camel@hpe.com> <20150903195134.GW8051@wotan.suse.de> <1441315902.3277.39.camel@hpe.com> <20150903220711.GX8051@wotan.suse.de> <1441319131.3277.54.camel@hpe.com> <20150903224556.GY8051@wotan.suse.de> <1441322474.3277.78.camel@hpe.com> <20150903235429.GZ8051@wotan.suse.de> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5 (3.16.5-1.fc22) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2015-09-04 at 01:54 +0200, Luis R. Rodriguez wrote: > On Thu, Sep 03, 2015 at 05:21:14PM -0600, Toshi Kani wrote: > > On Fri, 2015-09-04 at 00:45 +0200, Luis R. Rodriguez wrote: > > > On Thu, Sep 03, 2015 at 04:25:31PM -0600, Toshi Kani wrote: : > > > > On Xen, > > > > > > When Xen is used a platform firmware may still set up MTRR, even if the > > > hypervisor doesn't set up MTRR right ? So same issue and question here. > > > > Right, I meant to say Xen guests. > > Ah but its import complicated than that. > > > In case of the Xen hypervisor, > > mtrr_type_lookup() returns a valid type as it runs on a platform. > > I am not sure if this happens today, I know MTRR is simply disabled by > the Xen Hypervisor on the CPU explicitly, it disable it so guests reading > the MTRR capabilities sees it as disabled when queried. Oh, I would not let the hypervisor to disable MTRRs... > Then since the Xen Linux guests cannot speak MTRR through the hypervisor > (for instance Xen guests cannot ask Xen hypervisor to mtrr_type_lookup() for > it) if PCI passthrough is used it could mean a guest might set up / use > incorrect info as well. > > If I undestand this correctly then I think we're in a pickle with Xen unless > we add hypervisor support and hypercall support for mtrr_type_lookup(). I was under assumption that MTRRs are emulated and disabled on guests. Isn't guest physical address virtualized? I know other proprietary VMMs on IA64, but know nothing about Xen... So, please disregard my comments to Xen. :-) Thanks, -Toshi