I use latest revision of xen-unstable, kernel-2.6.32-4 from 'Debian Sid' and Debian Squeeze for Dom0.
I tried to create Opensolaris b132 DomU:

my config (i use config from http://blogs.sun.com/mrj/entry/installing_opensolaris_on):

>:# cat ns.pv_i
bootloader = "/usr/bin/pygrub"
kernel = "/platform/i86xpv/kernel/amd64/unix"
ramdisk = "/boot/x86.microroot"
extra = "/platform/i86xpv/kernel/amd64/unix -B console=ttya,livemode=text"
memory = 512
name = "OS_PV"
vif = [ 'mac=00:16:3E:00:00:01', 'mac=00:16:3E:00:00:02' ]
disk = [ 'file:/opt/ISO/osol-dev-132-x86.iso,6:cdrom,r', 'file:/opt/src/OS_PV/ns.img,0,w' ]
on_reboot = 'destroy'
on_crash = 'destroy'
on_poweroff = 'destroy'

>:# xm create ns.pv_i -c
Using config file "./ns.pv_i".
Error: Cannot find kernel "/platform/i86xpv/kernel/amd64/unix"

The method proposed by Boris Derzhavets works fine. (http://bderzhavets.wordpress.com/2010/04/14/zfs-24-support-via-pygrub-fsimage-iso-patch-for-xen-4-0-dom0-pvops-2-6-32-11-on-top-of-f12/).

p.s:
>:# pygrub /opt/ISO/osol-dev-132-x86.iso
linux (kernel /var/run/xend/boot/boot_kernel.GQYAjq)(ramdisk /var/run/xend/boot/boot_ramdisk.Q_bPCY)(args "/platform/i86xpv/kernel/amd64/unix")

Thanks.

2010/4/7 eXeC001er <execooler@gmail.com>
When this patch will be applied?

2010/3/27 Pasi Kärkkäinen <pasik@iki.fi>

On Sat, Mar 27, 2010 at 07:37:03AM -0400, Mark Johnson wrote:
> On Fri, Mar 19, 2010 at 3:40 PM, Mark Johnson <johnson.nh@gmail.com> wrote:
> > On Fri, Mar 19, 2010 at 2:41 PM, eXeC001er <execooler@gmail.com> wrote:
> >> Hi.
> >> When will be supported ZFS version more than 16 for pygrub?
> >> Current ZFS version is 22.
> >
> > I'm actively working on it  (current version is 24 now BTW).
>
> I pushed the patch to the OpenSolaris xvm-gate.
>     http://src.opensolaris.org/source/xref/xen-gate/xvm-gate+xen-patches.hg/fsimage-zfs-24
>
> I'll be testing to see if it builds/works on a Linux dom0 next week.
>

Great! This would be nice for Xen 4.0.0..

-- Pasi