linux-kernel - Re: [PATCH 1/1] tpm: disable hwrng for fTPM on some AMD designs

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Message-ID: <CAHk-=whPvSJH=H9eHZbJQ+sxC-AVDvrgJ+M14fD3K5A+5s=zVA@mail.gmail.com>
Date:   Mon, 31 Jul 2023 16:28:13 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Limonciello, Mario" <mario.limonciello@....com>
Cc:     linux@...inikbrodowski.net, Jarkko Sakkinen <jarkko@...nel.org>,
        Daniil Stas <daniil.stas@...teo.net>,
        James.Bottomley@...senpartnership.com, Jason@...c4.com,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        regressions@...mhuis.info, stable@...r.kernel.org
Subject: Re: [PATCH 1/1] tpm: disable hwrng for fTPM on some AMD designs

On Mon, 31 Jul 2023 at 14:57, Limonciello, Mario
<mario.limonciello@....com> wrote:
>
> Are you thinking then to unregister the tpm hwrng "sometime" after boot?

No, I was more thinking that instead of registering it as a randomness
source, you'd just do a one-time

    tpm_get_random(..);
    add_hwgenerator_randomness(..);

and leave it at that.

Even if there is some stutter due to some crazy firmware
implementation for reading the random data, at boot time nobody will
notice it.

           Linus