On Wed, 19 Sep 2018 10:18:39 +0200 David Hildenbrand <da...@redhat.com> wrote:
> My suggestion, either > a) Only use KVM_S390_VM_CPU_FEAT_AP to indicate/enable APIE statically > for the guest. > b) Only use KVM_S390_VM_CRYPTO_ENABLE_APIE to indicate/enable APIE > dynamically. > > Both things will be simple to implement. > > The difference really is that, with interface a), we will never be able > to support emulated devices in QEMU (as Christian mentioned, maybe that > is never the case). Because at the time the CPU model is configured, we > have no idea about which devices will get added. And we have to make a > decision (e.g. enable APIE) before creating CPUs and therefore before > creating AP devices. We will then need most probably a new interface > that allows us to enable/disable it dynamically. > > With b) however, we have more flexibility. We can defer the decision. Given that, I think I'd prefer b).