Editing QEMU (section)

===Xen-HVM===
[[Xen]], a virtual machine monitor, can run in HVM (hardware virtual machine) mode, using [[Intel VT-x]] or [[AMD-V]] hardware [[x86 virtualization]] extensions and [[ARM architecture|ARM]] [[ARM Cortex-A7|Cortex-A7]] and [[ARM Cortex-A15|Cortex-A15]] virtualization extensions.<ref name="ZfeJ33">{{cite web |title=Xen ARM with Virtualization Extensions |url=http://wiki.xenproject.org/wiki/Xen_ARM_with_Virtualization_Extensions}}</ref> This means that instead of para-virtualized devices, a real set of virtual hardware is exposed to the DomU, enabling it to use real device drivers.

QEMU includes several components: CPU emulators, emulated devices, generic devices, machine descriptions, user interface, and a debugger. The emulated devices and generic devices in QEMU make up its device models for I/O virtualization.<ref name="Fu2I73">{{cite web |title=Oracle and Sun Microsystems - Strategic Acquisitions - Oracle |url=http://www.sun.com/blueprints/1107/820-3703.pdf |website=www.sun.com}}</ref> They comprise a PIIX3 IDE (with some rudimentary PIIX4 capabilities), Cirrus Logic or plain VGA emulated video, RTL8139 or E1000 network emulation, and ACPI support.<ref name="29Ixu3">[http://ian.blenke.com/xen/hvm/svm/vtx/qemu Demystifying Xen HVM] {{webarchive|url=https://web.archive.org/web/20071222101854/http://ian.blenke.com/xen/hvm/svm/vtx/qemu|date=December 22, 2007}}</ref> APIC support is provided by Xen.

Xen-HVM utilizes device emulation based on the QEMU project to deliver I/O virtualization to virtual machines (VMs). Hardware is emulated through a QEMU "device model" daemon running as a backend in Dom0. Unlike other QEMU modes, such as dynamic translation or KVM, the hypervisor fully manages virtual CPUs, pausing them as necessary while QEMU handles memory-mapped I/O emulation.