https://wiki.archlinux.org/index.php/xen
The Xen hypervisor requires kernel level support which is included in recent Linux kernels and is built into the linux and linux-lts Arch kernel packages. To run HVM domU, the physical hardware must have either Intel VT-x or AMD-V (SVM) virtualization support. In order to verify this, run the following command when the Xen hypervisor is not running:
$ grep -E "(vmx|svm)" --color=always /proc/cpuinfo
If the above command does not produce output, then hardware virtualization support is unavailable and your hardware is unable to run HVM domU (or you are already running the Xen hypervisor). If you believe the CPU supports one of these features you should access the host system's BIOS configuration menu during the boot process and look if options related to virtualization support have been disabled. If such an option exists and is disabled, then enable it, boot the system and repeat the above command. The Xen hypervisor also supports PCI passthrough where PCI devices can be passed directly to the domU even in the absence of dom0 support for the device. In order to use PCI passthrough, the CPU must support IOMMU/VT-d.