Comment # 8 on bug 1021952 from lists dev

systemctl list-unit-files | egrep xen
    proc-xen.mount                          static
    var-lib-xenstored.mount                 static
    xen-dom0-modules.service                disabled
    xen-init-dom0.service                   enabled
    xen-qemu-dom0-disk-backend.service      enabled
    xen-watchdog.service                    disabled
    xencommons.service                      enabled
    xenconsoled.service                     enabled
???    xendomains.service                      disabled
    xendriverdomain.service                 disabled
    xenstored.service                       enabled

systemctl enable xendomains
shutdown -r now
    ...

xl list
    Name          ID   Mem VCPUs      State   Time(s)
    Domain-0       0  4096     1     r-----      51.7
    test           1  2049     1     -b----      16.2

Simple enought to fix.

Why xendomains.service

-- was disabled by the upgrade process
-- isn't (re)enabled by the (re)install/upgrade

is a question