The %%VirtFS%% driver was designed to work with QEMU's 9p server and does not work with bhyve's lib9p based 9p server.

There are some changes towards fixing this [[https://github.com/swills/virtfs-9p-kmod|on GitHub]] along with a [[https://github.com/swills/random-ports/tree/master/emulators/virtfs-9p-kmod|port]]