Re: [Qemu-devel] Re: [PATCH 1/2] allow hypervisor CPUID bit to be overriden

[Gleb Natapov]

On Wed, Jun 24, 2009 at 10:20:41PM +0100, Jamie Lokier wrote:
> Avi Kivity wrote:
> > 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.
> 
> Hold on.
> 
> Do the SVVP tests fail on a real (non-virtal) machine then?
> 
SVVP -> Server Virtualization Validation Program

Definitely fails on a real machine :)

--
                        Gleb.