As soon as I plug an nvme into my system I can't boot on zfs root (ZFS enabled bootstrap loader). I can load from DVD, and I've since reinstalled onto a temporary UFS root system and everything works fine.
The system freezes during the BTX loader screen, the drive is given a BIOS drive letter, then the spinner stops before the "Bios 625kB/3654644kB available memory" screen.
Some grepping brings me to this loop
Zfs appears to have its own dv_init here: https://svnweb.freebsd.org/base/release/10.3.0/sys/boot/zfs/zfs.c?revision=297553&view=markup#l385
From this point I hope someone might have a better idea than printf debugging :)
The nvme is a Samsung 950 pro, it's in a pcie m2 card. I can dig out exact model of mount if required.
nvme0: Samsung SSD 950 PRO 512GB
# diskinfo -v /dev/nvd0
512 # sectorsize
512110190592 # mediasize in bytes (477G)
1000215216 # mediasize in sectors
512 # stripesize
0 # stripeoffset
S2GMNCAGA01093W # Disk ident.
# pciconf -lv | grep nvme -A3
nvme0@pci0:3:0:0: class=0x010802 card=0xa801144d chip=0xa802144d rev=0x01 hdr=0x00
vendor = 'Samsung Electronics Co Ltd'
class = mass storage
subclass = NVM
re severity, I came across someone else with exact same problem on forums.