At the moment there two main features are being implemented for XEN support on AGL: Dom0 support on different boards and the DomU support. (https://jira.automotivelinux.org/browse/SPEC-3384 + https://jira.automotivelinux.org/browse/SPEC-3259).
Sometimes these features could be used separately (with different OS as dom0 or domu).
But the configuration when AGL is dom0 and domU simultenously is possible and it will be useful to have possibility to prepare full image for dom0 with included domU withing one build attempt.
It is proposed to consider MULTICONFIG feature of the yocto to implement that (see comment for https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/24560).