On 20.12.2009, at 18:23, Gleb Natapov wrote: > On Sun, Dec 20, 2009 at 07:18:22PM +0200, Michael S. Tsirkin wrote: >> On Sun, Dec 20, 2009 at 06:17:02PM +0100, Alexander Graf wrote: >>> >>> On 20.12.2009, at 17:56, Michael S. Tsirkin wrote: >>> >>>> On Sun, Dec 20, 2009 at 05:59:33PM +0200, Avi Kivity wrote: >>>>> On 12/20/2009 05:51 PM, Michael S. Tsirkin wrote: >>>>>> >>>>>>> Maybe we should make -cpu host the default. That will give the best >>>>>>> performance for casual users, more testing for newer features, and will >>>>>>> force management apps to treat migration much more seriously. The >>>>>>> downside is that casual users upgrading their machines might experience >>>>>>> issues with Windows. Feature compatibility is not just about migration. >>>>>>> >>>>>> This seems very aggressive. Can't we whitelist features that we know >>>>>> about? Further, doesn't KVM already do this? >>>>>> >>>>>> >>>>> >>>>> It does, but without -cpuid host you're stuck with qemu64 (kvm.ko >>>>> doesn't add features userspace didn't request). >>>> >>>> Hmm, then, shouldn't either kvm or qemu mask features that we do not >>>> emulate well enough to make windows not crash? >>> >>> -cpu host does that already, no? >>> >>> Alex >> >> I expected so, but Avi here seems to say windows will crash if you >> use a new CPU with it ... >> > Windows _may_ crash if you'll _upgrade_ your _host_ CPU.
Uh. It may lose activation I guess. But apart from that I can't see how it'd break as long as you don't expect loadvm to work. Anybody mind to go into a bit more detail here? :-) Alex
