My evidence is mostly anecdotal, unfortunately. Most of my experimentation was KVM in KVM from about 2012 and i saw frequent long pauses in the kernel, lockups,

My evidence is mostly anecdotal, unfortunately. Most of my experimentation was KVM in KVM from about 2012 and i saw frequent long pauses in the kernel, lockups, and kernel panics. At the time, the attitude from the qemu-kvm community was that it wasn't a high priority and that it may or may not work. It is possible that it is better now, but redhat's opinion[1] as of last year was still that it wasn't supported in production. I don't know if it is any better with other hypervisors. Last week, for example, I ran into an issue with nested virt in vmware fusion[2] that prevented me from running kvm in a guest. I would need a bunch of testing before I trusted it. It looks like xen has spotty support[3] as well. Amazon uses a heavily forked version of xen, so I suspect support for it is even worse on their version. (EDIT: added info on xen) [1]: https://www.redhat.com/en/blog/inception-how-usable-are-nested-kvm-guests https://www.redhat.com/en/blog/inception-how-usable-are-nest... [2]: https://bugs.launchpad.net/qemu/+bug/1661386 https://bugs.launchpad.net/qemu/+bug/1661386 [3]: https://wiki.xenproject.org/wiki/Nested_Virtualization_in_Xen https://wiki.xenproject.org/wiki/Nested_Virtualization_in_Xe...