See and

[R]emove [the] DVD device from [the] problem[atic] virtual machine:
# xe vm-list params=uuid name-label="<your-vm-name>"
# xe vbd-list empty=true params=uuid vm-uuid=<your-vm-UUID>
# xe vbd-destroy uuid=<vbd-UUID>

I can confirm the above steps really makes a FreeBSD stable/9 amd64 XENHVM kernel tick on XenServer 6.2.0.

stable/10 and head works out of the box without the need of removing the DVD drive. Yay!

Just remember to install the two ports sysutils/xen-tools and sysutils/xe-guest-utilities, and adding xenguest_enable="YES" to the /etc/rc.conf file.