From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932274Ab0E0UNS (ORCPT ); Thu, 27 May 2010 16:13:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:24762 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756045Ab0E0UNP (ORCPT ); Thu, 27 May 2010 16:13:15 -0400 Message-ID: <4BFED258.40501@redhat.com> Date: Thu, 27 May 2010 10:13:12 -1000 From: Zachary Amsden User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100430 Fedora/3.0.4-3.fc13 Thunderbird/3.0.4 MIME-Version: 1.0 To: Glauber Costa CC: Avi Kivity , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Add Documentation/kvm/msr.txt References: <1274897088-8587-1-git-send-email-glommer@redhat.com> <4BFE2A2F.50209@redhat.com> <20100527160248.GF3445@mothafucka.localdomain> In-Reply-To: <20100527160248.GF3445@mothafucka.localdomain> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/27/2010 06:02 AM, Glauber Costa wrote: > On Thu, May 27, 2010 at 11:15:43AM +0300, Avi Kivity wrote: > >> On 05/26/2010 09:04 PM, Glauber Costa wrote: >> >>> This patch adds a file that documents the usage of KVM-specific >>> MSRs. >>> >>> >> Looks good. A few comments: >> >> >>> + >>> +Custom MSR list >>> +-------- >>> + >>> +The current supported Custom MSR list is: >>> + >>> +MSR_KVM_WALL_CLOCK: 0x11 >>> + >>> + data: physical address of a memory area. >>> >> Which must be in guest RAM (i.e., don't point it somewhere random >> and expect the hypervisor to allocate it for you). >> >> Must be aligned to 4 bytes (we don't enforce it though). >> > I don't see the reason for it. > > If this is a requirement, our own implementation > is failing to meet it. > It's so the atomic write actually is atomic. Stating a 4 -byte alignment requirement prevents the wall clock from crossing a page boundary. Zach