Originally KVM set %eax to 0 in the cpuid leaf 0x4000000 rather than to the highest supported leaf in the hypervisor "branch". Detect this case and fixup the %eax value so that the hypervisor is still detected. Reported by: jpaetzel Reviewed by: kib MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D14810