linux-kernel - Re: [PATCH v8 07/11] tpm, tpm_tis: do not check for the active locality in interrupt handler

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Date:   Sun, 23 Oct 2022 07:32:24 +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, jandryuk@...il.com,
        pmenzel@...gen.mpg.de, l.sanfilippo@...bus.com, lukas@...ner.de,
        p.rosenberger@...bus.com
Subject: Re: [PATCH v8 07/11] tpm, tpm_tis: do not check for the active
 locality in interrupt handler

On Tue, Oct 18, 2022 at 01:57:28AM +0200, Lino Sanfilippo wrote:
> From: Lino Sanfilippo <l.sanfilippo@...bus.com>
> 
> After driver initialization tpm_tis_data->locality may only be modified in
> case of a LOCALITY CHANGE interrupt. In this case the interrupt handler
> iterates over all localities only to assign the active one to
> tpm_tis_data->locality.
> 
> However this information is never used any more, so the assignment is not
> needed.
> Furthermore without the assignment tpm_tis_data->locality cannot change any
> more at driver runtime, and thus no protection against concurrent
> modification is required when the variable is read at other places.
> 
> So remove this iteration entirely.
> 
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@...bus.com>

Acked-by: Jarkko Sakkinen <jarkko@...nel.org>

> ---
>  drivers/char/tpm/tpm_tis_core.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 181c291b0bb8..4336f7ea8c2b 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -728,7 +728,7 @@ static irqreturn_t tis_int_handler(int dummy, void *dev_id)
>  	struct tpm_chip *chip = dev_id;
>  	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
>  	u32 interrupt;
> -	int i, rc;
> +	int rc;
>  
>  	rc = tpm_tis_read32(priv, TPM_INT_STATUS(priv->locality), &interrupt);
>  	if (rc < 0)
> @@ -740,10 +740,7 @@ static irqreturn_t tis_int_handler(int dummy, void *dev_id)
>  	set_bit(TPM_TIS_IRQ_TESTED, &priv->flags);
>  	if (interrupt & TPM_INTF_DATA_AVAIL_INT)
>  		wake_up_interruptible(&priv->read_queue);
> -	if (interrupt & TPM_INTF_LOCALITY_CHANGE_INT)
> -		for (i = 0; i < 5; i++)
> -			if (check_locality(chip, i))
> -				break;
> +
>  	if (interrupt &
>  	    (TPM_INTF_LOCALITY_CHANGE_INT | TPM_INTF_STS_VALID_INT |
>  	     TPM_INTF_CMD_READY_INT))
> -- 
> 2.36.1
> 

BR, Jarkko