IncludeOS: a unikernel for C++ applications

It sounds like there's some logic to the design choice: not bothering to support multiple cores neatly sidesteps having to think about or write code for whole classes of problems - no need to handle scheduling, synchronisation or IPIs in every program, just pure computation and bit-banging virtio devices.

The downside is that ignoring the problems won't make most of them go away; to avoid side-channel attacks you'll need a whole air gap between instances, not a hypervisor.