linux-kernel - Re: MSI B350M MORTAR: tpm tpm0: AMD fTPM version 0x3005700000004 causes system stutter; hwrng disabled

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Message-ID: <ZJhVAX6b6bcZtguo@zx2c4.com>
Date:   Sun, 25 Jun 2023 16:53:53 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Paul Menzel <pmenzel@...gen.mpg.de>
Cc:     Mario Limonciello <mario.limonciello@....com>,
        linux-integrity@...r.kernel.org,
        Jarkko Sakkinen <jarkko@...nel.org>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Jason Gunthorpe <jgg@...pe.ca>, Peter Huewe <peterhuewe@....de>
Subject: Re: MSI B350M MORTAR: tpm tpm0: AMD fTPM version 0x3005700000004
 causes system stutter; hwrng disabled

On Sun, Jun 25, 2023 at 10:20:22AM +0200, Paul Menzel wrote:
> Thank you for your great work on the Linux kernel.
> 
> On an MSI MS-7A37/B350M MORTAR (MS-7A37) even updating to their latest 
> system firmware 1.O7 released on their Web site on May, 23rd 2023 [1].
> 
> > Beschreibung:
> > -  AGESA ComboAm4v2PI 1.2.0.A. update.
> > -  TPM Out of Bounds Access security patch.
> 
> But Linux 6.4.-rc7 still disables the hwrng from AMD fTPM.
> 
>      Jun 24 21:32:09.978772 tokeiihto kernel: DMI: Micro-Star 
> International Co., Ltd. MS-7A37/B350M MORTAR (MS-7A37), BIOS 1.O7 05/09/2023
>      […]
>      Jun 24 21:32:10.259986 tokeiihto kernel:  tpm tpm0: AMD fTPM 
> version 0x3005700000004 causes system stutter; hwrng disabled
> 
> Unfortunately, the warning does not say, what firmware version is 
> needed, and what the user can do about it.
> 
> The comment in the code, added in v6.3-rc2 with commit f1324bbc4011 
> (tpm: disable hwrng for fTPM on some AMD designs) [2], says:
> 
>      /*
>       * Some AMD fTPM versions may cause stutter
>       * https://www.amd.com/en/support/kb/faq/pa-410
>       *
>       * Fixes are available in two series of fTPM firmware:
>       * 6.x.y.z series: 6.0.18.6 +
>       * 3.x.y.z series: 3.57.y.5 +
>       */
> 
> Mapping 0x3005700000004 from the Linux warning to the comment, I assume 
> the board’s firmware is 3.57.0.4?
> 
> What AGESA ComboAm4v2PI would MSI need to ship, so the issue is fixed? 
> The previous system firmware version shipped 3.4e.0.4? (Is it decimal or 
> hexadecimal?)

Sounds like this is a question for MSI - why they haven't updated from
3.57.y.4 to 3.57.y.5+. What can we possibly say about this from a
Linux perspective? The Linux code apparently is working as designed by
avoiding using the buggy firmware gracefully.