From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH 4/9] Implement hsave v5 Date: Thu, 30 Oct 2008 15:44:57 -0500 Message-ID: <490A1CC9.3070600@codemonkey.ws> References: <1224522290-11740-1-git-send-email-agraf@suse.de> <1224522290-11740-2-git-send-email-agraf@suse.de> <1224522290-11740-3-git-send-email-agraf@suse.de> <1224522290-11740-4-git-send-email-agraf@suse.de> <1224522290-11740-5-git-send-email-agraf@suse.de> <4909F71E.2030306@codemonkey.ws> <4C0FB979-99A3-49AD-9AE5-DA2A066DC2E1@suse.de> <490A0AFE.2060202@redhat.com> <1797E4C8-3B35-4C40-864C-B410755AF0A2@suse.de> 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, joro@8bytes.org To: Alexander Graf Return-path: Received: from yw-out-2324.google.com ([74.125.46.29]:42327 "EHLO yw-out-2324.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753218AbYJ3UpC (ORCPT ); Thu, 30 Oct 2008 16:45:02 -0400 Received: by yw-out-2324.google.com with SMTP id 9so360011ywe.1 for ; Thu, 30 Oct 2008 13:45:01 -0700 (PDT) In-Reply-To: <1797E4C8-3B35-4C40-864C-B410755AF0A2@suse.de> Sender: kvm-owner@vger.kernel.org List-ID: Alexander Graf wrote: > > On 30.10.2008, at 20:29, Avi Kivity wrote: > >> Alexander Graf wrote: >>> >>> I don't see any benefit from actually exporting that MSR atm. KVM >>> does never read it and it'd just add additional overhead on every >>> userspace transition, as it'd need to be synced every time. >> >> We only sync MSRs on save/restore. > > Oh, really? Looks like I interpreted that code wrong :-). > Nevertheless, we don't use the hsave given by the guest OS, because we > can't trust it. So saving and restoring a non-used value sounds pretty > useless - unless you're migrating from KVM to Qemu. Is this kind of > migration (going to be) possible? But what if the guest tries to reread the hsave value it wrote? Couldn't that break a guest? Regards, Anthony Liguori > Alex >