AMD RDRAND

AMD RDRAND

[Germano Massullo]

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/

Re: AMD RDRAND

[Jason A. Donenfeld]

Hi Germano,

On Mon, Jan 11, 2021 at 10:54 PM Germano Massullo
<germano.massullo@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

Re: AMD RDRAND

[Germano Massullo]

Il 12/01/21 00:20, Jason A. Donenfeld ha scritto:
> Hi Germano,
>
> 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

Hi Jason, I did not know you already addressed the problem in the Linux
kernel, I just made a quick search in Wireguard mailing list but I did
not find any discussion related to RDRAND
I did not experience the problem (I haven't run proper tests yet), and I
haven't studied yet in detail all new replies in the thread. I just
wanted to let Wireguard developers know about this problem because I
thought it may affect Wireguard