On Tue, 05 Nov 2013 14:53:14 +0100 Andreas Färber <afaer...@suse.de> wrote:
> Am 05.11.2013 10:52, schrieb Paolo Bonzini: > > 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. > > PowerPC currently does not have -cpu option parsing. If you need to > implement it, I would ask for a generic hook in CPUClass set by > TYPE_POWERPC_CPU, so that the logic does not get hardcoded in cpu_init, > and for the p=v parsing logic to be so generic as to just set property p > to value v on the CPU instance. I.e. please make the compatibility > settings a static property or dynamic property of the CPU. Seconded, that's what is on my to-do list for x86 once x86 properties series is applied. moreover, all hook has to do is to translate -cpu to a set of global options, adding [CPUtype.foo, val] pairs to global option list. Then options will be automatically applied to any new instance of CPUtype and there won't be any need for accessing/storing cpu_model string during cpu creation and hotplug. > > Maybe the parsing code could even live in generic qom/cpu.c, overridden > by x86/sparc and reused for arm? Somewhere down my to-do list but > patches appreciated... > > Andreas >
