linux-kernel - Re: [PATCH] tpm: return false from tpm_amd_is_rng

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Date:   Fri, 30 Jun 2023 13:07:00 +0300
From:   "Jarkko Sakkinen" <jarkko@...nel.org>
To:     "Jerry Snitselaar" <jsnitsel@...hat.com>,
        <linux-kernel@...r.kernel.org>, <linux-integrity@...r.kernel.org>
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        "Jason Gunthorpe" <jgg@...pe.ca>,
        "Peter Huewe" <peterhuewe@....de>, <stable@...r.kernel.org>,
        "Linux regressions mailing list" <regressions@...ts.linux.dev>,
        "Mario Limonciello" <mario.limonciello@....com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        "Sachin Sant" <sachinp@...ux.ibm.com>
Subject: Re: [PATCH] tpm: return false from tpm_amd_is_rng_defective on
 non-x86 platforms

On Thu Jun 29, 2023 at 11:41 PM EEST, Jerry Snitselaar wrote:
> tpm_amd_is_rng_defective is for dealing with an issue related to the
> AMD firmware TPM, so on non-x86 architectures just have it inline and
> return false.
>
> Cc: Jarkko Sakkinen <jarkko@...nel.org>
> Cc: "Jason A. Donenfeld" <Jason@...c4.com>
> Cc: Jason Gunthorpe <jgg@...pe.ca>
> Cc: Peter Huewe <peterhuewe@....de>
> Cc: stable@...r.kernel.org
> Cc: Linux regressions mailing list <regressions@...ts.linux.dev>
> Cc: Mario Limonciello <mario.limonciello@....com>
> Reported-by: Aneesh Kumar K. V <aneesh.kumar@...ux.ibm.com>
> Reported-by: Sachin Sant <sachinp@...ux.ibm.com>
> Closes: https://lore.kernel.org/lkml/99B81401-DB46-49B9-B321-CF832B50CAC3@linux.ibm.com/
> Fixes: f1324bbc4011 ("tpm: disable hwrng for fTPM on some AMD designs")
> Signed-off-by: Jerry Snitselaar <jsnitsel@...hat.com>
> ---
>  drivers/char/tpm/tpm-chip.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index cd48033b804a..cf5499e51999 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -518,6 +518,7 @@ static int tpm_add_legacy_sysfs(struct tpm_chip *chip)
>   * 6.x.y.z series: 6.0.18.6 +
>   * 3.x.y.z series: 3.57.y.5 +
>   */
> +#ifdef CONFIG_X86
>  static bool tpm_amd_is_rng_defective(struct tpm_chip *chip)
>  {
>  	u32 val1, val2;
> @@ -566,6 +567,12 @@ static bool tpm_amd_is_rng_defective(struct tpm_chip *chip)
>  
>  	return true;
>  }
> +#else
> +static inline bool tpm_amd_is_rng_defective(struct tpm_chip *chip)
> +{
> +	return false;
> +}
> +#endif /* CONFIG_X86 */
>  
>  static int tpm_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
>  {
> -- 
> 2.38.1

Sanity check, this was the right patch, right?

I'll apply it.

BR, Jarkko