Problem with ZFS userboot changes r262331 and VM with mixed partitions

[Craig Rodrigues]

Hi,

I encountered problems with the new changes to userboot
to boot ZFS.

About a month ago, I created a FreeBSD 10 VM with the following
layout:

=>       34  419430333  md0  GPT  (200G)
         34        128    1  freebsd-boot  (64K)
        162    2097152    2  freebsd-ufs  (1.0G)
    2097314    8388608    3  freebsd-swap  (4.0G)
   10485922  408944444    4  freebsd-zfs  (195G)
  419430366          1       - free -  (512B)


The FreeBSD root file system is on p4, which is ZFS.
On the root file system, I have a symlink:

/boot -> /bootdir

/bootdir mounts p2 which is UFS.

So in this scenario, the kernel lives on UFS.
When I did this about a month ago, during the BHyve boot process,

(1)  userboot loaded the kernel from p2 (UFS)
(2)  The kernel booted, loaded zfs.ko, and then proceeded to mount p4 where
      the root file system lived (ZFS)

After r262331, when I try to boot the BHyve VM

(1)  I can see p4 from the loader prompt
(2)  The kernel doesn't load
(3)  If I try to load /boot/kernel/kernel from the loader prompt, I get:

ZFS: i/o error - all block copies unavailable

I don't fully understand all this logic.  Is there a bug that can be fixed here?

--
Craig