Customers who wish to upgrade existing Linux guests to versions which now operate in HVM mode (that is, RHEL 7, CentOS 7, and Ubuntu 14.04) should perform an in-guest upgrade. At this point, the upgraded Guest will only
run in PV mode - which is not supported and has known issues. Customers should run the following script to convert the newly upgraded guest to the supported HVM mode. To do this:
On the XenServer host, open a local shell, log on as root, and enter the following command:
/opt/xensource/bin/pv2hvm <vm_name>
or
/opt/xensource/bin/pv2hvm <vm_uuid>
Restart the VM to complete the process.