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? Or is QEMU's machine emulation insufficiently accurate? I see a drawback in setting the bit by default. Something I expect from an emulator is that it behaves like a real machine to the extent possible. In particular, guest code which attempts to check if it's running on a real machine should get the answer "yes". Unfriendly guest code which pops up a message like "Sorry I refuse to work for you after 100 hours/ because you are attempting to run me in a virtual machine, and don't even think of trying to hide this from me now you know I look for it" should never do so. -- Jamie -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
