Solved Using GRUB2 to chainload GELI-encrypted root on ZFS FreeBSD 10.1-RC2

[free-and-bsd]

The kfreebsd line is what makes my machine unresponsive

I used to have this problem with Linux versions of GRUB2, but not any more.

I can also try building https://github.com/dweeezil/grub.git from source and booting from that version of GRUB.

Well I've tried it yesterday with git://git.savannah.gnu.org/grub.git and all works just fine, no problem loading kernel.
However, I built it on my linux system, with the last git versions of SPL and ZFS installed, against which I built the last git version of GRUB2. It works perfectly well, only I haven't tried it with the new feature flags of ZFS, which come with 10.1-RELEASE.

I'm mentioning this, because after having upgraded the pool I lost the sysutils/grub2 functionality as it cannot read some of the zpool-features(7) (namely, com.delphix:embedded_data). This makes the pool pretty much inaccessible to GRUB2 in this case, so I'm not hasting to upgrade my existing pool, where 10.1-RELEASE is installed by upgrading process, while the pool itself was created using some "obsolete" utils a year ago.

But I'll check that in the office, where I've already upgraded all the pools. Theoretically, since this build of GRUB is linked against the latest ZFS libs, I don't see why it shouldn't read those feature flags... but who knows. In any case, we always have the BTX bootloader which will boot FreeBSD even from the most advanced pool. Then there is this option to recreate the pool using some of the recent FreeBSD releases, with earlier versions of ZFS there.
EDIT: it says at https://github.com/dweeezil/grub.git that this version does support feature flags... but it's worth testing.