After a recent kernel update for Centos 7.4, Paravirtualized DomUs under Xen stooped booting. They just crash on boot.
Apparently it seems a new restriction in RHEL 7 kernel. And there are some suggestions i found in different forums to switch to HVM or PVHM. Problem is that most of Paravirt DomUs are installed on plain disks (without partitions). But to convert them to HVM or PVHM they need Grub installed inside the VM which need partition table. So it is a full reinstallation :(
Centos guys say it is something RHEL need to fix. So is this a bug which can be fixed in near future ? or is that RHEL just dont want its kernel to run on Paravirt vms any more ?
Had the same issue, and as a hack workaround installed the CentOS Xen kernel before upgrading to 7.4. Had no issues booting with that kernel in place. If RedHat fixes their kernel it should be relatively simple to switch back to it.