The bhyve kernel module and its associated userland consumers have been updated
to the latest upstream FreeBSD sources as of:

commit f81459bd8363602ed5e436f10288320419e80ccf
Author: andrew <andrew@FreeBSD.org>
Date:   Thu Sep 27 11:16:19 2018 +0000

    Handle a guest executing a vm instruction by trapping and raising an
    undefined instruction exception. Previously we would exit the guest,
    however an unprivileged user could execute these.

    Found with:     syzkaller
    Reviewed by:    araujo, tychon (previous version)
    Approved by:    re (kib)
    MFC after:      1 week
    Differential Revision:  https://reviews.freebsd.org/D17192

Which corresponds to SVN revision: 338957