From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zachary Amsden Subject: Re: [PATCH] Add Documentation/kvm/msr.txt Date: Thu, 27 May 2010 10:13:12 -1000 Message-ID: <4BFED258.40501@redhat.com> References: <1274897088-8587-1-git-send-email-glommer@redhat.com> <4BFE2A2F.50209@redhat.com> <20100527160248.GF3445@mothafucka.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Avi Kivity , kvm@vger.kernel.org, linux-kernel@vger.kernel.org To: Glauber Costa Return-path: In-Reply-To: <20100527160248.GF3445@mothafucka.localdomain> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.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