From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [Qemu-devel] Re: [PATCH 1/2] allow hypervisor CPUID bit to be overriden Date: Tue, 23 Jun 2009 14:35:35 +0300 Message-ID: <4A40BE07.5080906@redhat.com> References: <1245707244-743-1-git-send-email-andre.przywara@amd.com> <4A40A7EC.8070100@redhat.com> <200906231231.15206.paul@codesourcery.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: qemu-devel@nongnu.org, Andre Przywara , aliguori@us.ibm.com, kvm@vger.kernel.org To: Paul Brook Return-path: Received: from mx2.redhat.com ([66.187.237.31]:57431 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755720AbZFWLgm (ORCPT ); Tue, 23 Jun 2009 07:36:42 -0400 In-Reply-To: <200906231231.15206.paul@codesourcery.com> Sender: kvm-owner@vger.kernel.org List-ID: On 06/23/2009 02:31 PM, Paul Brook wrote: > On Tuesday 23 June 2009, Avi Kivity wrote: > >> On 06/23/2009 12:47 AM, Andre Przywara wrote: >> >>> KVM defaults to the hypervisor CPUID bit to be set, whereas pure QEMU >>> clears it. On some occasions one want to set or clear it the other way >>> round (for instance to get HyperV running inside a guest). >>> Allow the default to be overridden on the command line and fix some >>> whitespace damage on the way. >>> >> It makes sense for qemu to set the hypervisor bit unconditionally. A >> guest running under qemu is not bare metal. >> > > I see no reason why a guest has to be told that it's running inside a VM. > In principle an appropriately configured qemu should be indistinguishable from > real hardware. In practice it's technically infeasible to cover absolutely > everything, but if we set this bit we're not even trying. > > I have no objection to the bit being set by default for the QEMU CPU types. > I agree it's pointless, but it is a Microsoft requirement for passing their SVVP tests. Enabling it by default makes life a little easier for users who wish to validate their hypervisor and has no drawbacks. -- error compiling committee.c: too many arguments to function