Re: [libvirt] [PATCH 0/7] x86: Rework KVM-defaults compat code, enable kvm_pv_unhalt by default

Now, I don't know yet what's the best default for a guest that has CONFIG_PARAVIRT_SPINLOCK when it sees a host that supports kvm_pv_unhalt. But I'm arguing that it's the guest responsibility to choose what to do when it detects such a host, instead of expecting the host to hide features from the guest. The guest and the guest administrator have more information to choose what's best. In other words, if exposing kvm_pv_unhalt on CPUID really makes some guests behave poorly, can we fix the guests instead?