Re: [PATCH v7 07/10] tmp, tmp_tis: Implement usage counter for locality

[Jarkko Sakkinen <jarkko@kernel.org>]

On Fri, Jul 01, 2022 at 02:29:47AM +0300, Jarkko Sakkinen wrote:
> On Thu, Jun 30, 2022 at 01:26:50AM +0200, Lino Sanfilippo wrote:
> > From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> > 
> > Implement a usage counter for the (default) locality used by the TPM TIS
> > driver:
> > Request the locality from the TPM if it has not been claimed yet, otherwise
> > only increment the counter. Also release the locality if the counter is 0
> > otherwise only decrement the counter. Ensure thread-safety by protecting
> > the counter with a mutex.
> > 
> > This allows to request and release the locality from a thread and the
> > interrupt handler at the same time without the danger to interfere with
> > each other.
> > 
> > By doing this refactor the names of the amended functions to use the proper
> > prefix.
> > 
> > Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> > Tested-by: Michael Niew??hner <linux@mniewoehner.de>
> > ---
> >  drivers/char/tpm/tpm_tis_core.c | 75 ++++++++++++++++++++++-----------
> >  drivers/char/tpm/tpm_tis_core.h |  2 +
> >  2 files changed, 53 insertions(+), 24 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> > index bd4eeb0b2192..e50a2c78de9f 100644
> > --- a/drivers/char/tpm/tpm_tis_core.c
> > +++ b/drivers/char/tpm/tpm_tis_core.c
> > @@ -165,16 +165,27 @@ static bool check_locality(struct tpm_chip *chip, int l)
> >  	return false;
> >  }
> >  
> > -static int release_locality(struct tpm_chip *chip, int l)
> > +static int tpm_tis_release_locality_locked(struct tpm_tis_data *priv, int l)
> > +{
> > +	tpm_tis_write8(priv, TPM_ACCESS(l), TPM_ACCESS_ACTIVE_LOCALITY);
> > +
> > +	return 0;
> > +}
> > +
> > +static int tpm_tis_release_locality(struct tpm_chip *chip, int l)
> >  {
> >  	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> >  
> > -	tpm_tis_write8(priv, TPM_ACCESS(l), TPM_ACCESS_ACTIVE_LOCALITY);
> > +	mutex_lock(&priv->locality_count_mutex);
> > +	priv->locality_count--;
> > +	if (priv->locality_count == 0)
> > +		tpm_tis_release_locality_locked(priv, l);
> > +	mutex_unlock(&priv->locality_count_mutex);
> >  
> >  	return 0;
> >  }
> >  
> > -static int request_locality(struct tpm_chip *chip, int l)
> > +static int tpm_tis_request_locality_locked(struct tpm_chip *chip, int l)
> >  {
> >  	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> >  	unsigned long stop, timeout;
> > @@ -215,6 +226,20 @@ static int request_locality(struct tpm_chip *chip, int l)
> >  	return -1;
> >  }
> >  
> > +static int tpm_tis_request_locality(struct tpm_chip *chip, int l)
> > +{
> > +	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> > +	int ret = 0;
> > +
> > +	mutex_lock(&priv->locality_count_mutex);
> > +	if (priv->locality_count == 0)
> > +		ret = tpm_tis_request_locality_locked(chip, l);
> > +	if (!ret)
> > +		priv->locality_count++;
> > +	mutex_unlock(&priv->locality_count_mutex);
> > +	return ret;
> > +}
> > +
> >  static u8 tpm_tis_status(struct tpm_chip *chip)
> >  {
> >  	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> > @@ -668,7 +693,7 @@ static int probe_itpm(struct tpm_chip *chip)
> >  	if (vendor != TPM_VID_INTEL)
> >  		return 0;
> >  
> > -	if (request_locality(chip, 0) != 0)
> > +	if (tpm_tis_request_locality(chip, 0) != 0)
> >  		return -EBUSY;
> >  
> >  	rc = tpm_tis_send_data(chip, cmd_getticks, len);
> > @@ -689,7 +714,7 @@ static int probe_itpm(struct tpm_chip *chip)
> >  
> >  out:
> >  	tpm_tis_ready(chip);
> > -	release_locality(chip, priv->locality);
> > +	tpm_tis_release_locality(chip, priv->locality);
> >  
> >  	return rc;
> >  }
> > @@ -751,7 +776,7 @@ static int tpm_tis_gen_interrupt(struct tpm_chip *chip)
> >  	cap_t cap;
> >  	int ret;
> >  
> > -	ret = request_locality(chip, 0);
> > +	ret = tpm_tis_request_locality(chip, 0);
> >  	if (ret < 0)
> >  		return ret;
> >  
> > @@ -760,7 +785,7 @@ static int tpm_tis_gen_interrupt(struct tpm_chip *chip)
> >  	else
> >  		ret = tpm1_getcap(chip, TPM_CAP_PROP_TIS_TIMEOUT, &cap, desc, 0);
> >  
> > -	release_locality(chip, 0);
> > +	tpm_tis_release_locality(chip, 0);
> >  
> >  	return ret;
> >  }
> > @@ -785,33 +810,33 @@ static int tpm_tis_probe_irq_single(struct tpm_chip *chip, u32 intmask,
> >  	}
> >  	priv->irq = irq;
> >  
> > -	rc = request_locality(chip, 0);
> > +	rc = tpm_tis_request_locality(chip, 0);
> >  	if (rc < 0)
> >  		return rc;
> >  
> >  	rc = tpm_tis_read8(priv, TPM_INT_VECTOR(priv->locality),
> >  			   &original_int_vec);
> >  	if (rc < 0) {
> > -		release_locality(chip, priv->locality);
> > +		tpm_tis_release_locality(chip, priv->locality);
> >  		return rc;
> >  	}
> >  
> >  	rc = tpm_tis_write8(priv, TPM_INT_VECTOR(priv->locality), irq);
> >  	if (rc < 0) {
> > -		release_locality(chip, priv->locality);
> > +		tpm_tis_release_locality(chip, priv->locality);
> >  		return rc;
> >  	}
> >  
> >  	rc = tpm_tis_read32(priv, TPM_INT_STATUS(priv->locality), &int_status);
> >  	if (rc < 0) {
> > -		release_locality(chip, priv->locality);
> > +		tpm_tis_release_locality(chip, priv->locality);
> >  		return rc;
> >  	}
> >  
> >  	/* Clear all existing */
> >  	rc = tpm_tis_write32(priv, TPM_INT_STATUS(priv->locality), int_status);
> >  	if (rc < 0) {
> > -		release_locality(chip, priv->locality);
> > +		tpm_tis_release_locality(chip, priv->locality);
> >  		return rc;
> >  	}
> >  
> > @@ -819,11 +844,11 @@ static int tpm_tis_probe_irq_single(struct tpm_chip *chip, u32 intmask,
> >  	rc = tpm_tis_write32(priv, TPM_INT_ENABLE(priv->locality),
> >  			     intmask | TPM_GLOBAL_INT_ENABLE);
> >  	if (rc < 0) {
> > -		release_locality(chip, priv->locality);
> > +		tpm_tis_release_locality(chip, priv->locality);
> >  		return rc;
> >  	}
> >  
> > -	release_locality(chip, priv->locality);
> > +	tpm_tis_release_locality(chip, priv->locality);
> >  	clear_bit(TPM_TIS_IRQ_TESTED, &priv->flags);
> >  
> >  	/* Generate an interrupt by having the core call through to
> > @@ -959,8 +984,8 @@ static const struct tpm_class_ops tpm_tis = {
> >  	.req_complete_mask = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
> >  	.req_complete_val = TPM_STS_DATA_AVAIL | TPM_STS_VALID,
> >  	.req_canceled = tpm_tis_req_canceled,
> > -	.request_locality = request_locality,
> > -	.relinquish_locality = release_locality,
> > +	.request_locality = tpm_tis_request_locality,
> > +	.relinquish_locality = tpm_tis_release_locality,
> >  	.clk_enable = tpm_tis_clkrun_enable,
> >  };
> >  
> > @@ -994,6 +1019,8 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
> >  	priv->timeout_min = TPM_TIMEOUT_USECS_MIN;
> >  	priv->timeout_max = TPM_TIMEOUT_USECS_MAX;
> >  	priv->phy_ops = phy_ops;
> > +	priv->locality_count = 0;
> > +	mutex_init(&priv->locality_count_mutex);
> >  
> >  	dev_set_drvdata(&chip->dev, priv);
> >  
> > @@ -1071,14 +1098,14 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
> >  
> >  	intmask &= ~TPM_GLOBAL_INT_ENABLE;
> >  
> > -	rc = request_locality(chip, 0);
> > +	rc = tpm_tis_request_locality(chip, 0);
> >  	if (rc < 0) {
> >  		rc = -ENODEV;
> >  		goto out_err;
> >  	}
> >  
> >  	tpm_tis_write32(priv, TPM_INT_ENABLE(priv->locality), intmask);
> > -	release_locality(chip, 0);
> > +	tpm_tis_release_locality(chip, 0);
> >  
> >  	rc = tpm_chip_start(chip);
> >  	if (rc)
> > @@ -1112,13 +1139,13 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
> >  		 * proper timeouts for the driver.
> >  		 */
> >  
> > -		rc = request_locality(chip, 0);
> > +		rc = tpm_tis_request_locality(chip, 0);
> >  		if (rc < 0)
> >  			goto out_err;
> >  
> >  		rc = tpm_get_timeouts(chip);
> >  
> > -		release_locality(chip, 0);
> > +		tpm_tis_release_locality(chip, 0);
> >  
> >  		if (rc) {
> >  			dev_err(dev, "Could not get TPM timeouts and durations\n");
> > @@ -1138,11 +1165,11 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
> >  			dev_err(&chip->dev, FW_BUG
> >  					"TPM interrupt not working, polling instead\n");
> >  
> > -			rc = request_locality(chip, 0);
> > +			rc = tpm_tis_request_locality(chip, 0);
> >  			if (rc < 0)
> >  				goto out_err;
> >  			disable_interrupts(chip);
> > -			release_locality(chip, 0);
> > +			tpm_tis_release_locality(chip, 0);
> >  		}
> >  	}
> >  
> > @@ -1209,13 +1236,13 @@ int tpm_tis_resume(struct device *dev)
> >  	 * an error code but for unknown reason it isn't handled.
> >  	 */
> >  	if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
> > -		ret = request_locality(chip, 0);
> > +		ret = tpm_tis_request_locality(chip, 0);
> >  		if (ret < 0)
> >  			return ret;
> >  
> >  		tpm1_do_selftest(chip);
> >  
> > -		release_locality(chip, 0);
> > +		tpm_tis_release_locality(chip, 0);
> >  	}
> >  
> >  	return 0;
> > diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
> > index e005eb99480e..7c6c14707e31 100644
> > --- a/drivers/char/tpm/tpm_tis_core.h
> > +++ b/drivers/char/tpm/tpm_tis_core.h
> > @@ -91,6 +91,8 @@ enum tpm_tis_flags {
> >  
> >  struct tpm_tis_data {
> >  	u16 manufacturer_id;
> > +	struct mutex locality_count_mutex;
> > +	unsigned int locality_count;
> >  	int locality;
> >  	int irq;
> >  	unsigned int int_mask;
> > -- 
> > 2.25.1
> > 
> 
> I'm kind of thinking that should tpm_tis_data have a lock for its
> contents?
> 
> I kind of doubt that we would ever need more than one lock for it,
> and it would give some more ensurance to not be race, especially
> when re-enabling interrupts this feels important to be "extra safe".
> 
> I looked at this commit, and did not see anything that would prevent
> using a spin lock instead of mutex. With a spin lock priv can be
> accessed also in the interrupt context.
> 
> So instead prepend this patch with a patch that adds:
> 
>         struct spin_lock lock;
> 
> And something like:
> 
>         static inline struct tpm_tis_data *tpm_tis_priv_get(struct tpm_chip *chip)
>         {
>                 struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> 
>                 spin_lock(&priv->lock); 
>                 return priv; 
>         }
> 
>         static inline void tpm_tis_priv_put(struct tpm_tis_data *priv)
>         {
>                 spin_unlock(&priv->lock);
>         }
> 
> And change the sites where priv is used to acquire the instance with this.

I.e.

        struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);

becomes:

        struct tpm_tis_data *priv = tpm_tis_priv_get(&chip);

In some simes most likely the acquirance must be done later, e.g.
because of locking order with chip's lock (perhaps).

BR, Jarkko