Il 05/11/2013 11:27, Alexander Graf ha scritto: > > 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.
Agreed. Paolo
