Re: [PATCH] riscv: Work to remove kernel dependence on the M-extension

[Christoph Hellwig]

On Wed, Mar 09, 2022 at 11:34:25PM -0800, Palmer Dabbelt wrote:
> If someone has hardware that lacks M and users care about running Linux on
> that then I'm happy to support it.  I'll still point out the silliness of
> that decision, but if it's too late to change things then I'd rather support
> the hardware.  If it's one of these "fill out every possible allowed ISA
> flavor, even if nobody has one that runs Linux" then I don't see a reason to
> bother -- there's an infinite amount of allowable RISC-V implementations,
> we'll all go crazy chasing them around.

It's not like Linux had required M mode since the RISC-V port was merged
upstream, so any new implementor really should know about it.  And
performance on anything that requires Linux will just be horrible.
I could see a bit of an excuse for a nommu port.

Anyway, this kind of patch really does need to state the why.  And it
better be a really good reason.