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

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Date: Tue, 4 Jun 2024 16:04:15 -0700
From: ross.philipson@...cle.com
To: Jarkko Sakkinen <jarkko@...nel.org>, 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, ross.philipson@...cle.com
Subject: Re: [PATCH v9 16/19] tpm: Add ability to set the preferred locality
 the TPM chip uses

On 6/4/24 3:50 PM, Jarkko Sakkinen wrote:
> 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.

Ok got it, thanks.

> 
> BR, Jarkko
>