[libvirt] cannot start a qemu64 model on an Intel host

Dan Kenigsberg danken at redhat.com
Mon Apr 12 19:32:46 UTC 2010


On Wed, Jan 06, 2010 at 10:38:32AM +0100, Jiri Denemark wrote:
> > If I specify
> > 
> > <cpu match="exact">
> >     <model>qemu64</model>
> > </cpu>
> > 
> > according to the new cpu schema, I get
> >     error: internal error guest CPU is not compatible with host CPU
> > because qemu64 supports svm, and my host does not.
> > 
> > However, the error remains when I explicitly ask to disable svm with
> >     <feature policy="disable" name="svm"/>
> > 
> > I am not sure if this is a bug or an intended feature, but I'd expect
> > cpu_disable taken into account when doing
> >     x86ModelCompare(host_model, cpu_require)
> 
> It is a bug. There's no sense in checking features which will be disabled
> anyway.
> 
> Thanks for reporting.

Only today was I told of another issue with specifying:
     <model>qemu64</model>
     <feature policy="disable" name="svm"/>

libvirt's algorithm ends up setting

-cpu qemu32,+lm,+nx,+syscall,+cx16,+ssse3,+clflush,+pse36,+mca,+mtrr

which is quite different (particularily if you intend to run 64 bit
guests), and certainly no what you'd expect with match="expect".

Regards,

Dan.




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