BHyVe is dependent for now upon Intel VT-x virtualization support on modern CPUs while AMD SVM support is still being developed. BHyVe also depends upon other modern features like Extended Page Tables and VirtIO. It's making its debut in FreeBSD 10.0 but does support guests going back to FreeBSD 8.3. Right now though this is the only operating systems supported in an unmodified state.
BHyVe currently has IOAPIC emulation, memory-mapped local APIC support, guest idle detection, and some level of AHCI emulation. Still being worked out with this FreeBSD hypervisor is removing blocking I/O operations, suspend/resume support, AMD SVM, and support for older GPUs without nested paging virtualization.
With taking advantage of modern CPU functionality and software features, the BHyVe implementation between its kernel module, library, and user-space utilities amount to about 250 thousand lines of code. The code was merged into FreeBSD head in just the middle of January.
BHyVe was talked about last weekend at FOSDEM 2013 during the BSD track and more details on this open-source hypervisor can be found out on the FreeBSD Wiki and bhyve.org. This BSD hypervisor isn't nearly as advance or feature-complete as Linux KVM or Xen, but at least it's moving along and improving the BSD world.