That was the point behind Singularity OS[1] IIRC. Using managed code which could be verified safe by the OS using static analysis.
Can't find it right now, but I recall reading they implemented a network driver with minimal overhead compared to a traditional OS. While they used message passing, a lot of overhead could be eliminated due to the assumptions of safe code.
Message passing by itself doesn't have to be slow (you can use the paging subsystem for this purpose), but you are looking at two more context switches per system call.
Can't find it right now, but I recall reading they implemented a network driver with minimal overhead compared to a traditional OS. While they used message passing, a lot of overhead could be eliminated due to the assumptions of safe code.
[1]: https://en.wikipedia.org/wiki/Singularity_%28operating_syste...