From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MJ4J1-0002TJ-JT for qemu-devel@nongnu.org; Tue, 23 Jun 2009 07:36:52 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MJ4Iw-0002P1-0L for qemu-devel@nongnu.org; Tue, 23 Jun 2009 07:36:50 -0400 Received: from [199.232.76.173] (port=42164 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MJ4Iv-0002Ok-0N for qemu-devel@nongnu.org; Tue, 23 Jun 2009 07:36:45 -0400 Received: from mx2.redhat.com ([66.187.237.31]:42685) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1MJ4Iu-00069L-JQ for qemu-devel@nongnu.org; Tue, 23 Jun 2009 07:36:44 -0400 Message-ID: <4A40BE07.5080906@redhat.com> Date: Tue, 23 Jun 2009 14:35:35 +0300 From: Avi Kivity MIME-Version: 1.0 Subject: Re: [Qemu-devel] Re: [PATCH 1/2] allow hypervisor CPUID bit to be overriden References: <1245707244-743-1-git-send-email-andre.przywara@amd.com> <4A40A7EC.8070100@redhat.com> <200906231231.15206.paul@codesourcery.com> In-Reply-To: <200906231231.15206.paul@codesourcery.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paul Brook Cc: Andre Przywara , aliguori@us.ibm.com, qemu-devel@nongnu.org, kvm@vger.kernel.org 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