From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v2][uq/master] kvm: x86: Save/restore FPU OP, IP and DP Date: Sun, 19 Jun 2011 15:58:53 +0300 Message-ID: <4DFDF28D.3030206@redhat.com> References: <4DF33413.9070605@web.de> <4DF8B0E6.1080806@siemens.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , kvm , qemu-devel To: Jan Kiszka Return-path: Received: from mx1.redhat.com ([209.132.183.28]:42598 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753507Ab1FSM7B (ORCPT ); Sun, 19 Jun 2011 08:59:01 -0400 In-Reply-To: <4DF8B0E6.1080806@siemens.com> Sender: kvm-owner@vger.kernel.org List-ID: On 06/15/2011 04:17 PM, Jan Kiszka wrote: > These FPU states are properly maintained by KVM but not yet by TCG. So > far we unconditionally set them to 0 in the guest which may cause > state corruptions, though not with modern guests. > > To avoid breaking backward migration, use a conditional subsection that > is only written if any of the three fields is non-zero. The guest's > FNINIT clears them frequently, and cleared IA32_MISC_ENABLE MSR[2] > reduces the probability of non-zero values further so that this > subsection is not expected to restrict migration in any common scenario. Thanks, applied to uq/master. A test migration showed that the subsection in fact did not show up. -- error compiling committee.c: too many arguments to function