From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33347) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XHHUb-0002vy-9w for qemu-devel@nongnu.org; Tue, 12 Aug 2014 15:12:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XHHUQ-0004tH-9n for qemu-devel@nongnu.org; Tue, 12 Aug 2014 15:12:21 -0400 Received: from mail-wi0-x234.google.com ([2a00:1450:400c:c05::234]:48968) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XHHUQ-0004t1-2x for qemu-devel@nongnu.org; Tue, 12 Aug 2014 15:12:10 -0400 Received: by mail-wi0-f180.google.com with SMTP id n3so6263793wiv.13 for ; Tue, 12 Aug 2014 12:12:09 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <53EA6700.2060603@redhat.com> Date: Tue, 12 Aug 2014 21:12:00 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <538EC63A.80405@redhat.com> <20140812185552.GJ3011@thinpad.lan.raisama.net> In-Reply-To: <20140812185552.GJ3011@thinpad.lan.raisama.net> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] Qemu: Fix eax for cpuid leaf 0x40000000 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost , Jidong Xiao Cc: qemu-devel@nongnu.org, KVM Il 12/08/2014 20:55, Eduardo Habkost ha scritto: > This makes the CPUID data change under the guest's feet during > live-migration. > > Adding compat code to ensure older machine-types keep the old behavior > is necessary, but in this specific case it is mostly harmless because > 0x0 is documented as being equivalent to 0x40000001. > > (But I don't know how guests are supposed to behave when they see > CPUID[KVM_CPUID_SIGNATURE_NEXT].EAX==0.) The only obvious thing to do would be to treat it as 0x40000101. Paolo