as per @grehan:
> There's now another UEFI update - had to put this one out quick since without it, Linux kernels >= 4.15 won't boot properly in bhyve :(
>
> I also rolled in a CSM/BIOS bugfix from Illumos.
see [PR 227765](https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=227765)