AMD RDRAND

[Jason A. Donenfeld]

Hi Germano,

On Mon, Jan 11, 2021 at 10:54 PM Germano Massullo
<germano.massullo at gmail.com> wrote:
>
> I would like to inform Wireguard developers about the following.
> it seems that this [1] old AMD RDRAND problem is still present:
> RDRAND on AMD Ryzen 9 5900X is flakey -
> https://github.com/systemd/systemd/issues/18184
>
> I own 2x Ryzen 3600, feel free to write me in case you would like to run
> some tests
>
> [1]:
> https://arstechnica.com/gadgets/2019/10/how-a-months-old-amd-microcode-bug-destroyed-my-weekend/

I fixed this already, by removing the use of RDRAND from
get_random_{u32,u64,int,long} entirely:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=69efea712f5b0489e67d07565aad5c94e09a3e52

This happened almost a year ago back in February, and was backported
to the stable kernels too, which means you should have no issues
finding a working kernel for your brand new Ryzen.

Is this actually a problem you're experiencing or is your report
mostly just speculation based on that systemd issue you linked to?

Jason