Re: Linux in VirtualPC in KVM fails

Avi Kivity
2009-01-09T19:34:41Z

Alexander Graf wrote:
>> We're in a nice compatibility mess. We can't just switch paravirt
>> detection methods since that will break older guests _and_ older
>> hosts on non-nested virtualization (which is the common case).
>
> Shouldn't it be ok to push patches to linux-stable to use the CPUID
> and MSR information and simply not expose the CPUID identification in
> newer KVM versions? That way older guests on newer KVM don't use KVM
> paravirt (which should still be ok), but everything else runs as
> smoothly as possible.

No. It's a regression (esp. kvmclock).

It's perfectly legitimate to say we support Virtual PC beginning some
kvm version (and to supply the command line workaround for older
versions). But we shouldn't knowingly break existing setups.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.