It reminds me a wee bit of stuff that has happened in browsers. NaCl was a way to run untrusted native code by scanning it for unsafe operations. BPF seems to

It reminds me a wee bit of stuff that has happened in browsers. NaCl was a way to run untrusted native code by scanning it for unsafe operations. BPF seems to have a similar aim in a sense: run less-trustworthy code in an unrestricted environment, but don't use CPU hardware based access control (and therefore context switching) to limit it, rather, make the code more sandboxed in software to prevent the need for context switches.