[notnarb]

SmartOS has code specifically in place for using 'lx' branded zones as wrappers for docker containers (which is distinct from its support of kvm)

https://github.com/joyent/smartos-live/blob/master/src/docke...

https://www.cruwe.de/2016/01/27/using-docker-on-smartos-hype...

It's been a while since I've looked in to it, but if memory serves they are using docker filesystem snapshots without modification and running them on a thin translation layer of Linux system calls to Solaris system calls. Hard to find anything backing this up, so I could be way off the mark as to how it's implemented.

EDIT: forgot that's what 'lx' zones are: zones which allow the execution of Linux binaries