There is a specification of privileged extensions, I think it was stabilised fairly recently: https://people.eecs.berkeley.edu/~krste/papers/riscv-priv-spec-1.

There is a specification of privileged extensions, I think it was stabilised fairly recently: https://people.eecs.berkeley.edu/~krste/papers/riscv-priv-spec-1.7.pdf https://people.eecs.berkeley.edu/~krste/papers/riscv-priv-sp... The rocket chip generator https://github.com/ucb-bar/rocket-chip https://github.com/ucb-bar/rocket-chip and boom both have support for it, as far as I know.