If you are like me, using the pci_hda audio on FreeBSD 12 (12.2 in my case). Make sure to cherry-pick the following commit:
b151e337: Fix the register layout for the Buffer Descript List Entry.
Without that commit, the pci_hda might fail on certain guests with the following message:
Assertion failed: (!(bdle_sz % HDA_DMA_ACCESS_LEN)), function hda_stream_start, file /usr/src/usr.sbin/bhyve/pci_hda.c, line 686