>>> >>> In this case we will have no problem with older guests not having idea >>> about APXA. >>> >>> Would it be a solution? >> >> Any feature the guest sees, should be part of the CPU model. The whole >> environment for cpu subfunctions is already in place both in KVM and >> QEMU. Only disabling subfunctions in KVM is not implemented yet. >> >> You can exclude any subfunctions/facilities that are only valid on LPAR >> level and cannot be used in some guest either way. (that makes life >> sometimes easier) >> >> >> I know that this might sound a little bit complicated, but it really >> isn't. Boils down to modifying kvm_s390_cpu_feat_init() and specifying >> some features+feature groups in QEMU. > > OK, we definitively need another patch/patch-set, to handle this. > Do you think it can be done in another series since if we always support > APXA when we have AP instructions, we already have an indication that > APXA exist: the AP facility. > Please implement the subfunction stuff right away. This will allow to handle all future facilities transparently from a kernel POV. Implementing that should be easy - and I don't like gluing features together in such a way. You can always assure that consistent data (e.g. AP + APXA availability) is reported from KVM to QEMU. > Regards, > Pierre > > > > -- Thanks, David / dhildenb
