bhyve, as used in FreeBSD through 12.1 and illumos (e.g., OmniOS CE through r151034 and OpenIndiana through Hipster 2020.04), does not properly restrict VMCS and VMCB read/write operations, as demonstrated by a root user in a container on an Intel system, who can gain privileges by modifying VMCS_HOST_RIP.
https://security.netapp.com/advisory/ntap-20201016-0002/
https://security.FreeBSD.org/advisories/FreeBSD-SA-20:28.bhyve_vmcs.asc