Re: [Qemu-devel] cpuid problem in upstream qemu with kvm

[Michael S. Tsirkin]

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 ...

-- 
MST