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Date: Fri, 1 Jul 2022 02:29:44 +0300
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Lino Sanfilippo <LinoSanfilippo@....de>
Cc: peterhuewe@....de, jgg@...pe.ca, stefanb@...ux.vnet.ibm.com,
linux@...ewoehner.de, linux-integrity@...r.kernel.org,
linux-kernel@...r.kernel.org, l.sanfilippo@...bus.com,
lukas@...ner.de, p.rosenberger@...bus.com
Subject: Re: [PATCH v7 07/10] tmp, tmp_tis: Implement usage counter for
locality
On Thu, Jun 30, 2022 at 01:26:50AM +0200, Lino Sanfilippo wrote:
> From: Lino Sanfilippo <l.sanfilippo@...bus.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@...bus.com>
> Tested-by: Michael Niew??hner <linux@...ewoehner.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.
BR, Jarkko
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