Hi, I am having the same issue. After upgrade to 4.9.0-7-amd64 from 4.9.0-6-amd64 my xen vm they stop working.
I run xenserver 6.2 and as a temporal fix I just convert the VM to HVM from PV xe vm-param-set uuid=YOURVMUID HVM-boot-policy="BIOS order" PV-bootloader="" So looks like running in Hardware-assisted Virtualization (HVM) helps
