linux-kernel - Re: [BUG] Non working HWRNG on AMD Ryzen 5 5500GT

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Message-ID: <0561862d-99d9-ae72-49d0-9ad0639482ea@amd.com>
Date: Thu, 15 Aug 2024 09:16:45 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Diederik de Haas <didi.debian@...ow.org>, John Allen <john.allen@....com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>,
 "David S. Miller" <davem@...emloft.net>, linux-crypto@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [BUG] Non working HWRNG on AMD Ryzen 5 5500GT

On 8/15/24 08:56, Diederik de Haas wrote:
> Hi,
> 
> I recently bought an Asus ROG STRIX B550-F GAMING MB with an
> AMD Ryzen 5 5500GT CPU (and installed the latest BIOS: 3607).
> I'm running Debian Testing/Sid on it with kernel 6.9 and now 6.10
> and it seems to work great.
> I've been doing some (unrelated) tests with `rngtest` from the
> `rng-tools5` package and wondered how it would fare on my AMD CPU.

I'm not very familiar with this test. What is the command line that you
are using to invoke it?

> 
> And I found out it doesn't work at all!
> But on another system I have (Asus ROG CROSSHAIR VII HERO MB +
> AMD Ryzen 1800X CPU) it works absolutely fine.
> 
> # dmesg | grep ccp
> [    5.399853] ccp 0000:07:00.2: ccp: unable to access the device: you might
> be running a broken BIOS.
> [    5.401031] ccp 0000:07:00.2: tee enabled
> [    5.401113] ccp 0000:07:00.2: psp enabled

Which system is this output from?

Can you provide the output from lspci -nn?

Thanks,
Tom

> 
> Found an article [1] which could be relevant and downloaded and ran the
> accompanying test program (written by Jason Donenfeld):
> # ./amd-rdrand-bug
> Your RDRAND() does not have the AMD bug.
> # ./test-rdrand
> RDRAND() =x47c993c0
> RDRAND() =xec7c697d
> ... (more seemingly random numbers)
> RDRAND() =xba858101
> 
> I tried it with the latest microcode dd 2024-07-10, but that didn't make
> a difference.
> 
> So I'd like to know if this may actually be a bug on the kernel side.
> 
> Happy to provide additional information or run tests or try patches.
> 
> Cheers,
>   Diederik
> 
> [1] https://arstechnica.com/gadgets/2019/10/how-a-months-old-amd-microcode-bug-destroyed-my-weekend/