linux-kernel - Re: [PATCH v9 16/19] tpm: Add ability to set the preferred locality the TPM chip uses

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Message-Id: <D1RIKP548WG9.Q5MM7K3FRH4P@kernel.org>
Date: Tue, 04 Jun 2024 23:27:09 +0300
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Ross Philipson" <ross.philipson@...cle.com>,
 <linux-kernel@...r.kernel.org>, <x86@...nel.org>,
 <linux-integrity@...r.kernel.org>, <linux-doc@...r.kernel.org>,
 <linux-crypto@...r.kernel.org>, <kexec@...ts.infradead.org>,
 <linux-efi@...r.kernel.org>, <iommu@...ts.linux-foundation.org>
Cc: <dpsmith@...rtussolutions.com>, <tglx@...utronix.de>,
 <mingo@...hat.com>, <bp@...en8.de>, <hpa@...or.com>,
 <dave.hansen@...ux.intel.com>, <ardb@...nel.org>, <mjg59@...f.ucam.org>,
 <James.Bottomley@...senpartnership.com>, <peterhuewe@....de>,
 <jgg@...pe.ca>, <luto@...capital.net>, <nivedita@...m.mit.edu>,
 <herbert@...dor.apana.org.au>, <davem@...emloft.net>, <corbet@....net>,
 <ebiederm@...ssion.com>, <dwmw2@...radead.org>, <baolu.lu@...ux.intel.com>,
 <kanth.ghatraju@...cle.com>, <andrew.cooper3@...rix.com>,
 <trenchboot-devel@...glegroups.com>
Subject: Re: [PATCH v9 16/19] tpm: Add ability to set the preferred locality
 the TPM chip uses

On Fri May 31, 2024 at 4:03 AM EEST, Ross Philipson wrote:
> Curently the locality is hard coded to 0 but for DRTM support, access
> is needed to localities 1 through 4.
>
> Signed-off-by: Ross Philipson <ross.philipson@...cle.com>
> ---
>  drivers/char/tpm/tpm-chip.c      | 24 +++++++++++++++++++++++-
>  drivers/char/tpm/tpm-interface.c | 15 +++++++++++++++
>  drivers/char/tpm/tpm.h           |  1 +
>  include/linux/tpm.h              |  4 ++++
>  4 files changed, 43 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 854546000c92..73eac54d61fb 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -44,7 +44,7 @@ static int tpm_request_locality(struct tpm_chip *chip)
>  	if (!chip->ops->request_locality)
>  		return 0;
>  
> -	rc = chip->ops->request_locality(chip, 0);
> +	rc = chip->ops->request_locality(chip, chip->pref_locality);
>  	if (rc < 0)
>  		return rc;
>  
> @@ -143,6 +143,27 @@ void tpm_chip_stop(struct tpm_chip *chip)
>  }
>  EXPORT_SYMBOL_GPL(tpm_chip_stop);
>  
> +/**
> + * tpm_chip_preferred_locality() - set the TPM chip preferred locality to open
> + * @chip:	a TPM chip to use
> + * @locality:   the preferred locality
> + *
> + * Return:
> + * * true      - Preferred locality set
> + * * false     - Invalid locality specified
> + */
> +bool tpm_chip_preferred_locality(struct tpm_chip *chip, int locality)
> +{
> +	if (locality < 0 || locality >=TPM_MAX_LOCALITY)
> +		return false;
> +
> +	mutex_lock(&chip->tpm_mutex);
> +	chip->pref_locality = locality;
> +	mutex_unlock(&chip->tpm_mutex);
> +	return true;
> +}
> +EXPORT_SYMBOL_GPL(tpm_chip_preferred_locality);
> +
>  /**
>   * tpm_try_get_ops() - Get a ref to the tpm_chip
>   * @chip: Chip to ref
> @@ -374,6 +395,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
>  	}
>  
>  	chip->locality = -1;
> +	chip->pref_locality = 0;
>  	return chip;
>  
>  out:
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index 5da134f12c9a..35f14ccecf0e 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -274,6 +274,21 @@ int tpm_is_tpm2(struct tpm_chip *chip)
>  }
>  EXPORT_SYMBOL_GPL(tpm_is_tpm2);
>  
> +/**
> + * tpm_preferred_locality() - set the TPM chip preferred locality to open
> + * @chip:	a TPM chip to use
> + * @locality:   the preferred locality
> + *
> + * Return:
> + * * true      - Preferred locality set
> + * * false     - Invalid locality specified
> + */
> +bool tpm_preferred_locality(struct tpm_chip *chip, int locality)
> +{
> +	return tpm_chip_preferred_locality(chip, locality);
> +}
> +EXPORT_SYMBOL_GPL(tpm_preferred_locality);

 What good does this extra wrapping do?

 tpm_set_default_locality() and default_locality would make so much more
 sense in any case.

 BR, Jarkko