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

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Date: Wed, 05 Jun 2024 01:50:27 +0300
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: <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 Wed Jun 5, 2024 at 1:14 AM EEST,  wrote:
> On 6/4/24 1:27 PM, Jarkko Sakkinen wrote:
> > 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.
>
> Are you mainly just talking about my naming choices here and in the 
> follow-on response? Can you clarify what you are requesting?

I'd prefer:

1. Name the variable as default_locality.
2. Only create a single expored to function to tpm-chip.c:
   tpm_chip_set_default_locality().
3. Call this function in all call sites.

"tpm_preferred_locality" should be just removed, as tpm_chip_*
is exported anyway.

BR, Jarkko