Hi,
Original propolis architect here, and primary engineer for much of the effort porting bhyve to illumos.<p>Quite a bit was changed between "illumos bhyve" and FreeBSD upstream. We in illumos decided to take a slightly different approach in how we approached the machinery for saving/restoring the state of devices emulated in-kernel, which is a necessary part of doing such a live migration. FreeBSD was first to add that functionality, but we (I) felt it exposed too much in the way of implementation details from that device emulation, rather than a more abstract model of the emulated hardware. It was at that point that illumos "soft-forked" the kernel VMM component so we could take a different approach. While the two kernel VMM components are very similar, and much of the bhyve userspace emulation (a counterpart to propolis) will run on either OS, there are some key differences around instruction emulation and those kernel-emulated devices which prevent them from being drop-in replacements for each other.<p>All that said, I'm happy to see FreeBSD making progress on this front. They've been a friendly peer in this space, and both projects benefit from efforts in this area.