On 05.11.2013, at 10:52, Paolo Bonzini <pbonz...@redhat.com> wrote: > Il 05/11/2013 10:16, Alexander Graf ha scritto: >> >> On 05.11.2013, at 10:06, Paolo Bonzini <pbonz...@redhat.com> wrote: >> >>> Il 30/09/2013 14:57, Alexey Kardashevskiy ha scritto: >>>>>> Why is the option under -machine instead of -cpu? >>>> Because it is still the same CPU and the guest will still read the real >>>> PVR from the hardware (which it may not support but this is why we need >>>> compatibility mode). >>> >>> How do you support migration from a newer to an older CPU then? I think >>> the guest should never see anything about the hardware CPU model. >> >> POWER can't model that. It always leaks the host CPU information into the >> guest. It's the guest kernel's responsibility to not expose that change to >> user space. >> >> Yes, it's broken :). I'm not even sure there is any sensible way to do live >> migration between different CPU types. > > Still in my opinion it should be "-cpu", not "-machine". Even if it's > just a "virtual" CPU model.
The only thing that this really changes is an SPR (MSR in x86 speech) on an existing cpu model. It's definitely not a new CPU type. If anything it'd be an option to an existing type. Alex
