From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [Qemu-devel] [PATCH] Qemu: Fix eax for cpuid leaf 0x40000000 Date: Tue, 12 Aug 2014 21:12:00 +0200 Message-ID: <53EA6700.2060603@redhat.com> References: <538EC63A.80405@redhat.com> <20140812185552.GJ3011@thinpad.lan.raisama.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: qemu-devel@nongnu.org, KVM To: Eduardo Habkost , Jidong Xiao Return-path: Received: from mail-wi0-f178.google.com ([209.85.212.178]:61757 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753925AbaHLTMK (ORCPT ); Tue, 12 Aug 2014 15:12:10 -0400 Received: by mail-wi0-f178.google.com with SMTP id hi2so6272950wib.17 for ; Tue, 12 Aug 2014 12:12:09 -0700 (PDT) In-Reply-To: <20140812185552.GJ3011@thinpad.lan.raisama.net> Sender: kvm-owner@vger.kernel.org List-ID: 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