Open Stack

On Tue, Feb 21, 2017 at 10:08:54AM -0500, David Medberry wrote:
> Doesn't the virtio solution assume/require a libvirt or more exactly a
> QEMU/KVM based hypervisor?
> 
> What about the N-1 other hypervisors?

vsock is an equivalent of UNIX domain sockets, for host<->guest communication
that was invented by VMWare.  KVM adopted the same socket protocol and layers
it over virtio. So from an application developer POV, whether you use VMWare
or KVM, vsock works the same way.  From a technology POV it wouldbe possible
to use vsock over virtio with Xen, since Xen supports the virtio bus, but I
doubt XenAPI will support it any time soon. Likewise I doubt hyperv will
support it, but they may well provide an equivalent alternatie, since this
is a commonly needed concept.

> I think the idea of a "hot remove, hot add" of the configdrive has some
> merit (but remember it is not always ISO-9660 but could be VFAT as well to
> aid in some migrations.)

NB current config drive is not well suited to hot remove. If using CDROM
with ISO-9660 you the guest to unlock the CDROM tray before the host is
able to eject & change media in it.  If using virtio disk with vfat, you
need the guest to honour ACPI request to unplug the PCI device. If the
disk is mounted, this unplug will not complete.

So realistically you'd need to change to use USB disks, which the host is
able to rip out from under the guest unconditionally, even if it is mountd
by the guest. Albeit with the caveat that the guest now needs to clean
up dangling mount points.

Regards,
Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://entangle-photo.org       -o-    http://search.cpan.org/~danberr/ :|