00-xl-create.txt

gadget xen # xl create -c /etc/xen/archlinux.cfg
Parsing config from /etc/xen/archlinux.cfg
libxl: warning: libxl_dm.c:350:libxl__domain_device_construct_rdm: Ignoring RDM conflict at 0x7c4bf000.

libxl: error: libxl_device.c:952:device_backend_callback: unable to add device with path /local/domain/0/backend/vbd/12/51712
libxl: error: libxl_create.c:1174:domcreate_launch_dm: unable to add disk devices
libxl: error: libxl_dm.c:2004:libxl__destroy_device_model: xs_rm failed for /local/domain/0/device-model/12
libxl: error: libxl_dm.c:1956:kill_device_model: unable to find device model pid in /local/domain/12/image/device-model-pid
libxl: error: libxl.c:1628:libxl__destroy_domid: libxl__destroy_device_model failed for 12
libxl: error: libxl_device.c:952:device_backend_callback: unable to remove device with path /local/domain/0/backend/vbd/12/51712
libxl: error: libxl.c:1665:devices_destroy_cb: libxl__devices_destroy failed for 12
libxl: error: libxl.c:1591:libxl__destroy_domid: non-existant domain 12
libxl: error: libxl.c:1549:domain_destroy_callback: unable to destroy guest with domid 12
libxl: error: libxl.c:1476:domain_destroy_cb: destruction of domain 12 failed

archlinux.cfg

builder='hvm'
memory=8192
name='archlinux'
vcpus=6
#bios=ovmf
acpi=1
apic=1
on_xend_stop='shutdown'
#vif = [ 'mac=00:16:3e:68:e1:01,bridge=xenbr0' ]
disk = [ '/dev/zvol/tank/arch,raw,xvda,rw' ]
#, '/root/archlinux-2015.10.01-dual.iso,raw,hdc,devtype=cdrom' ]
device_model_version = 'qemu-xen'
boot='cd'
usb=0
sdl=0
vnc=1
stdvga=1
serial='pty'
#gfx_passthru=1
#pci=[ '03:00.0', '03:00.1', '00:14.0' ]
rdm='strategy=host,policy=relaxed'
localtime=1
pci_power_mgmt=1

xl-info.txt

gadget xen # xl info
host                   : gadget
release                : 4.2.4-gentoo
version                : #1 SMP Wed Oct 28 20:19:45 2015
machine                : x86_64
nr_cpus                : 12
max_cpu_id             : 11
nr_nodes               : 1
cores_per_socket       : 6
threads_per_core       : 2
cpu_mhz                : 2394
hw_caps                : bfebfbff:2c100800:00000000:00006f00:77fefbff:00000000:00000021:000037ab
virt_caps              : hvm hvm_directio
total_memory           : 98202
free_memory            : 92846
sharing_freed_memory   : 0
sharing_used_memory    : 0
outstanding_claims     : 0
free_cpus              : 0
xen_major              : 4
xen_minor              : 6
xen_extra              : .0
xen_version            : 4.6.0
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          :
xen_commandline        : console=com1 com1=115200 loglvl=all dom0_mem=4096M,max:4096M
cc_compiler            : x86_64-pc-linux-gnu-gcc (Funtoo 4.9.3) 4.9.3
cc_compile_by          :
cc_compile_domain      : (none)
cc_compile_date        : Wed Oct 28 00:35:19  2015
xend_config_format     : 4
gadget xen # uname -a
Linux gadget 4.2.4-gentoo #1 SMP Wed Oct 28 20:19:45 2015 x86_64 Intel(R) Xeon(R) CPU E5-2620 v3 @ 2.40GHz GenuineIntel GNU/Linux

Have you solved that problem? I'm having exactly the same issue, and google brought me here.