Why are many "bare kernel+app" solutions targeting xen?

Question

There's a number of projects that produce complete images from your app, bootable on xen as a machine. For example Erlang on Xen, OpenMirage, HaLVM, and others.

Why is Xen the default hypervisor for them? Does it provide some interface that makes these projects easier (as opposed to KVM, VmWare, etc.), or is it just the project developers' choice?

Answer 1

Are Cloud Operating Systems the Next Big Thing? gives the following answer:

• Xen’s footprint in the Cloud: with AWS, Rackspace Public Cloud and many others running Xen, supporting Xen first makes sense.

• Xen Paravirtualization provides a very simple and idealized interface for I/O to the guest. In contrast, the KVM VIRTIO interface looks pretty much like the underlying hardware. As a consequence, it is easier to port a language runtime to Xen.