Usually you configure the VM to only report CPUID values corresponding to lowest-common-denominator features on everything you might want to migrate to. Then as

Usually you configure the VM to only report CPUID values corresponding to lowest-common-denominator features on everything you might want to migrate to. Then as long as the guest code plays nicely and looks at the CPUID feature flags to see what it can use, it'll migrate happily. QEMU has support for this, for instance.