Hi,
i converted LXC conf to xml by:

lxcuser@blade1:~/.local/share/lxc/test_deb$ virsh -c lxc:/// domxml-from-native lxc-tools /home/lxcuser/.local/share/lxc/test_deb/config

<domain type='lxc'>
<name>test_deb</name>
<uuid>cce77799-89fd-41fd-99c1-101e00844e23</uuid>
<memory unit='KiB'>65536</memory>
<currentMemory unit='KiB'>65536</currentMemory>
<vcpu placement='static'>1</vcpu>
<os>
<type arch='x86_64'>exe</type>
<init>/sbin/init</init>
</os>
<idmap>
<uid start='1258512' target='0' count='65536'/>
<gid start='1258512' target='0' count='65536'/>
</idmap>
<features>
<capabilities policy='allow'>
</capabilities>
</features>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>destroy</on_crash>
<devices>
<emulator>/usr/lib/libvirt/libvirt_lxc</emulator>
<filesystem type='mount' accessmode='passthrough'>
<source dir='/home/lxcuser/.local/share/lxc/test_deb/rootfs'/>
<target dir='/'/>
</filesystem>
<interface type='bridge'>
<mac address='00:16:3e:ab:21:1b'/>
<source bridge='br0'/>
<link state='up'/>
</interface>
</devices>
</domain>

Now attempt to define by virsh gives this err:

lxcuser@blade1:~/.local/share/lxc/test_deb$ virsh -c lxc:/// define tmp/test_deb.xml
error: Failed to define domain from /tmp/test_deb.xml
error: unsupported configuration: You must map the root user of container

Debian stretch.
Where am I wrong ?