Hi, I may be running into the same issue here, running Xen.
I say "may", because after I updated to Debian 9.5 and linux 4.9.0-7-amd64, the server/Dom0 did not come back up after a reboot, and I had to request a manual reboot from datacenter staff. The staff did not provide any more error details from the console other than that the OS failed to boot. I also did not find anything useful or relevant in logs, so I cannot provide more information. They rebooted it into a rescue-mode for me to login and fix it, from there I made grub boot Xen with the previous linux 4.9.0-6-amd64 kernel and the system came back up normally. The Xen virtual machines/DomUs themselves, however, do seem to run just fine with linux 4.9.0-7-amd64.
