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

[Avi Kivity]

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.

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