[my123]

> There is also the x86 memory ordering extension used by Rosetta 2.

That one isn't really a requirement either, and is handled fully in kernel mode.

Wkdm and friends are handled fully in kernel mode.

APRR? Not a strict requirement for user-mode, JIT regions are just left as RWX without it.

[saagarjha]

Apple enforces APRR on macOS; you need to use their APIs to work within the confines of W^X.