On my box:
# dmesg | grep -i xen
Xen: 0000000000000000 - 0000000020800000 (usable)
Kernel command line: root=/dev/xvda xencons=tty console=tty1 console=hvc0 nosep nodevfs ramdisk_size=32768 ip_conntrack.hashsize=8192 nf_conntrack.hashsize=8192 ro
Xen reported: 2500.088 MHz processor.
xen_mem: Initialising balloon driver.
Xen virtual console successfully installed as tty1
xen-vbd: registered block device major 202
XENBUS: Device with no driver: device/console/0
There are probably some similar traces of the virtualization solution you are using whichever it is.