You forgot to load xen backend modules. Guest domains will boot, but
are waiting for the host (dom0) to provide device implementations.
modprobe xen-netback
modprobe xen-pciback
modprobe xen-blkback
And while you're at it,
modprobe xen-gntdev
modprobe xen-gntalloc
modprobe xen-acpi-processor
Also, if you're using systemd,
cat << EOF > /etc/modules-load.d/xen.conf
xen-blkback
xen-netback
xen-pciback
xen-gntalloc
xen-gntdev
xen-acpi-processor
tmem
EOF