Re: [PATCH v6 08/17] riscv: use fallback for random_get_entropy() instead of zero

From: Palmer Dabbelt
Date: Mon Apr 25 2022 - 11:20:16 EST

On Mon, 25 Apr 2022 08:02:49 PDT (-0700), Jason@xxxxxxxxx wrote:
Hi Palmer,

On Mon, Apr 25, 2022 at 4:55 PM Palmer Dabbelt <palmer@xxxxxxxxxxx> wrote:
Fine for me if this goes in via some other tree, but also happy to take
it via the RISC-V tree if you'd like.

I'm going to take this series through the random.git tree, as I've got
things that build on top of it for random.c slated for 5.19.

IMO we could just call this a
fix, maybe

Fixes: aa9887608e77 ("RISC-V: Check clint_time_val before use")

(but that just brought this back, so there's likely older kernels broken
too). Shouldn't be breaking any real hardware, though, so no rush on my

That'd be fine with me, but it'd involve also backporting the
timekeeping patch, which adds a new API, so maybe we better err on the
side of caution with that new code.

wFM. Like I said this isn't going to break any existing hardware, and anyone trying to ship something without the timers is likely going to be in for way more trouble than this so will probably be stuck with newer kernels anyway.

Acked-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Reviewed-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>

Thanks for the review.

Makes sense: we had an architecturally-mandated timer at the time, but
we don't any more.

That's too bad. Out of curiosity, what happened? Was that deemed too
expensive for certain types of chips that western digital wanted to
produce for their hard drives, or some really constrained use case
like that?

No idea, but it was at the beginning of the "everything is optional"-ification of the ISA so I'm guessing it's just part of that.