It's definitely possible to do correctly, but looking through the code for both crates it doesn't look like they take the necessary precautions (issuing a fence or using RDTSCP). Which is a little weird because at least quanta explicitly checks for RDTSCP support, but then doesn't seem to use it.
(I'm not a Rust expert and I'm on my phone though, so I might be missing something.)
(I'm not a Rust expert and I'm on my phone though, so I might be missing something.)