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References: <20220629232653.1306735-1-LinoSanfilippo@gmx.de> <20220629232653.1306735-8-LinoSanfilippo@gmx.de>
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From:   Jason Andryuk <jandryuk@gmail.com>
Date:   Mon, 11 Jul 2022 15:39:15 -0400
Message-ID: <CAKf6xpvY1peO-mWM+bjaHnXhrqpOrGbyrOOaT18-myWYSJ88Sw@mail.gmail.com>
Subject: Re: [PATCH v7 07/10] tmp, tmp_tis: Implement usage counter for locality
To:     Lino Sanfilippo <LinoSanfilippo@gmx.de>
Cc:     Peter Huewe <peterhuewe@gmx.de>,
        Jarkko Sakkinen <jarkko@kernel.org>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Stefan Berger <stefanb@linux.vnet.ibm.com>,
        linux@mniewoehner.de, linux-integrity@vger.kernel.org,
        open list <linux-kernel@vger.kernel.org>,
        l.sanfilippo@kunbus.com, lukas@wunner.de, p.rosenberger@kunbus.com
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Hi,

This patch subject has a typo "tmp, tmp_tis" -> "tpm, tpm_tis"

On Wed, Jun 29, 2022 at 7:28 PM Lino Sanfilippo <LinoSanfilippo@gmx.de> wro=
te:
>
> 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, otherwi=
se
> 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 prop=
er
> prefix.
>
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> Tested-by: Michael Niew=C3=B6hner <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_c=
ore.c
> index bd4eeb0b2192..e50a2c78de9f 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c

> @@ -215,6 +226,20 @@ static int request_locality(struct tpm_chip *chip, i=
nt l)
>         return -1;
>  }
>
> +static int tpm_tis_request_locality(struct tpm_chip *chip, int l)
> +{
> +       struct tpm_tis_data *priv =3D dev_get_drvdata(&chip->dev);
> +       int ret =3D 0;
> +
> +       mutex_lock(&priv->locality_count_mutex);
> +       if (priv->locality_count =3D=3D 0)
> +               ret =3D tpm_tis_request_locality_locked(chip, l);
> +       if (!ret)
> +               priv->locality_count++;
> +       mutex_unlock(&priv->locality_count_mutex);
> +       return ret;
> +}
> +

This function should check that the requested locality matches the
current locality otherwise this sequence would seemingly succeed
though locality 0 is the one acquired.

tpm_tis_request_locality(chip, 0);
tpm_tis_request_locality(chip, 1);

Regards,
Jason