On Tue, Dec 04, 2018 at 07:16:39PM +0000, Peter Maydell wrote: > On Tue, 4 Dec 2018 at 19:05, Eduardo Habkost <ehabk...@redhat.com> wrote: > > On Tue, Dec 04, 2018 at 06:24:19PM +0000, Peter Maydell wrote: > > > A cluster is a group of CPUs which are all identical and have > > > the same view of the rest of the system. > > > With that definition in mind, why can't QEMU cluster CPUs > > automatically by looking at CPU models and address space objects? > > That sounds like it is in theory feasible and in practice > quite tricky. You would have to look not just at the CPU > model name but also introspect all its properties for > ones which change features of the CPU and are set differently > on different CPUs (and I don't think there's any way to > automatically tell which properties are ones which make > the CPU different for which-cluster purposes and which aren't). > And if we automatically checked whether address space objects > were the same it would rule out implementing devices with > per-cpu banked memory mapped registers by mapping different > things into the AS for each CPU (though that's a hypothetical > at the moment -- I've thought about implementing stuff that > way but we tend to implement that sort of thing by looking > at current_cpu->cpu_index at the moment).
I see. Can't we at least do something to make sure the cluster objects make sense? e.g. by ensuring at least QOM CPU type is the same, and that cpu->address_space somehow points to cpu->cluster->address_space? CCing Paolo, so he can correct me if this doesn't make sense. -- Eduardo
