Author Archives: jfehlig

libvirt support for Xen’s new libxenlight toolstack

Originally posted on my blog, here.

Xen has had a long history in libvirt.  In fact, it was the first hypervisor supported by libvirt.  I’ve witnessed an incredible evolution of libvirt over the years and now not only does it support managing many hypervisors such as Xen, KVM/QEMU, LXC, VirtualBox, hyper-v, ESX, etc., but it also supports managing a wide range of host subsystems used in a virtualized environment such as storage pools and volumes, networks, network interfaces, etc.  It has really become the swiss army knife of virtualization management on Linux, and Xen has been along for the entire ride.

libvirt supports multiple hypervisors via a hypervisor driver interface, which is defined in $LIBVIRT_ROOT/src/drvier.h – see struct _virDriver.  libvirt’s virDomain* APIs map to functions in the hypervisor driver interface, which are implemented by the various hypervisor drivers.  The drivers are located under $LIBVIRT_ROOT/src/<hypervisor-name>.  Typically, each driver has a $LIBVIRT_ROOT/src/<hypervisor-name>/<hypervisor-name>_driver.c file which defines a static instance of virDriver and fills in the functions it implements.  As an example, see the definition of libxlDriver in $libvirt_root/src/libxl/libxl_driver.c, the firsh few lines of which are

static virDriver libxlDriver = {
    .no = VIR_DRV_LIBXL,
    .name = “xenlight”,
    .connectOpen = libxlConnectOpen, /* 0.9.0 */
    .connectClose = libxlConnectClose, /* 0.9.0 */
    .connectGetType = libxlConnectGetType, /* 0.9.0 */
    ...
}

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