Hello,

With the help of Nikita, I've figured out how to get rid of
"xvda: unknown partition table"

I have to use /dev/xvda1 not the /dev/xvda

-------------------------------------
disk   = ['phy:/dev/vg01/vm0,xvda,w']
root   = '/dev/xvda ro'
-------------------------------------

changed to:

-------------------------------------
disk   = ['phy:/dev/vg01/vm0,xvda1,w']
root   = '/dev/xvda1 ro'
-------------------------------------

Anyway booting freezes. Once I've saw:

-------------------------------------
TCP cubic registered
XENBUS: Waiting for devices to initialise: 295s...290s...285s...280s...275s...270s...265s...260s...255s...250s...245s...240s...235s...230s...225s...220s...215s...210s...205s...200s...195s...190s...185s...180s...175s...170s...165s...160s...155s...150s...145s...140s...135s...130s...125s...120s...115s...110s...105s...100s...95s...90s...85s...80s...75s...70s...65s...60s...55s...50s...45s...40s...35s...30s...25s...20s...15s...10s...5s...0s...
XENBUS: Timeout connecting to device: device/vbd/51713 (local state 3, remote state 1)
XENBUS: Timeout connecting to device: device/vif/0 (local state 1, remote state 1)
VFS: Cannot open root device "xvda1" or unknown-block(0,0)
Please append a correct "root=" boot option; here are the available partitions:
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
Pid: 1, comm: swapper/0 Not tainted 3.2.12-gentoo #2
Call Trace:
 [<ffffffff81318ebd>] ? panic+0x92/0x199
 [<ffffffff81319004>] ? printk+0x40/0x4c
 [<ffffffff814f4e2e>] ? mount_block_root+0x238/0x24f
 [<ffffffff814f4fc0>] ? prepare_namespace+0x12c/0x156
 [<ffffffff814f4b3e>] ? kernel_init+0x10a/0x113
 [<ffffffff8131d074>] ? kernel_thread_helper+0x4/0x10
 [<ffffffff8131bd33>] ? int_ret_from_sys_call+0x7/0x1b
 [<ffffffff8131b43c>] ? retint_restore_args+0x5/0x6
 [<ffffffff8131d070>] ? gs_change+0x13/0x13
-------------------------------------

So I guess may be it's related to some DomU kernel configuration
problem? I've attached it to this letter.

test # cat .config | grep XEN
CONFIG_XEN=y
CONFIG_XEN_DOM0=y
CONFIG_XEN_PRIVILEGED_GUEST=y
CONFIG_XEN_PVHVM=y
CONFIG_XEN_MAX_DOMAIN_MEMORY=128
CONFIG_XEN_SAVE_RESTORE=y
# CONFIG_XEN_DEBUG_FS is not set
CONFIG_PCI_XEN=y
CONFIG_XEN_PCIDEV_FRONTEND=y
CONFIG_XEN_BLKDEV_FRONTEND=y
CONFIG_NETXEN_NIC=m
CONFIG_XEN_NETDEV_FRONTEND=y
CONFIG_HVC_XEN=y
CONFIG_XEN_BALLOON=y
CONFIG_XEN_BALLOON_MEMORY_HOTPLUG=y
CONFIG_XEN_SCRUB_PAGES=y
CONFIG_XEN_DEV_EVTCHN=y
# CONFIG_XEN_BACKEND is not set
CONFIG_XENFS=y
CONFIG_XEN_COMPAT_XENFS=y
CONFIG_XEN_SYS_HYPERVISOR=y
CONFIG_XEN_XENBUS_FRONTEND=y
CONFIG_XEN_GNTDEV=m
CONFIG_XEN_GRANT_DEV_ALLOC=m
CONFIG_SWIOTLB_XEN=y

-- 
Konstantin