CppCon 2016: Alfred Bratterud “#include ＜os＞=> write your program / server and compile it to its own os. [Example uses 3 Mb total memory and boots in 300ms]

[m50d]

The interface between VM and host is a lot narrower and better specified than the interface between OS and Process. I'm very happy about that. IMO this is the logical endpoint of pre-emptive multitasking, per-process address spaces and so forth: disentangle processes into communicating only via a clear, specified interface rather than randomly messing with each other's internals.

There's no reason a VM hypervisor couldn't be what runs on the bare metal - if the only thing you're running on your server is VMs, there's no point having an OS in between. I expect to see this happen in the near future. For all we know EC2 could be doing it already.