https://lkml.org/lkml/2022/9/19/640
Get at least down to here:
https://lkml.org/lkml/2022/9/20/1342
What Linus seems to be getting at is that there are many varying contextual restrictions on what code can do in different parts of the kernel, that Filho etc appear to be attempting to hide that complexity using language features, and that in his opinion it is not workable to fit kernel APIs into Rust's common definition of a single kind of "safe" code. All of this makes sense, in user land you don't normally have to care about things like whether different functional units are turned on or off, how interrupts are set up, etc, but in kernel you do. I'm not sure if Rust's macros and type system will allow solving the problem as Linus frames it but it seems like a worthy target & will be interesting to watch.