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

[Alexander Graf]

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