Hi,I'm facing this issue too on a fsc PRIMERGY RX300 S7. But when I limit the number of cpu's in dom0 the system boots into xen 4.8 with strecht Standard kernel.
(My Custom bulid 4.2 Kernel is working without this limitation) add:xen_commandline : placeholder dom0_mem=2048M,max:4096M dom0_max_vcpus=4 dom0_vcpus_pin
according to: https://wiki.debian.org/Xen#Other_configuration_tweaks -- Regards Joachim
