Re: [PATCH v2 2/5] tpm_tis: Clean up locality release

[Jarkko Sakkinen <jarkko@kernel.org>]

On Sat, Oct 24, 2020 at 03:10:07PM +0300, Jarkko Sakkinen wrote:
> On Mon, Oct 19, 2020 at 04:17:59PM -0700, Jerry Snitselaar wrote:
> > 
> > James Bottomley @ 2020-10-01 11:09 MST:
> > 
> > > The current release locality code seems to be based on the
> > > misunderstanding that the TPM interrupts when a locality is released:
> > > it doesn't, only when the locality is acquired.
> > >
> > > Furthermore, there seems to be no point in waiting for the locality to
> > > be released.  All it does is penalize the last TPM user.  However, if
> > > there's no next TPM user, this is a pointless wait and if there is a
> > > next TPM user, they'll pay the penalty waiting for the new locality
> > > (or possibly not if it's the same as the old locality).
> > >
> > > Fix the code by making release_locality as simple write to release
> > > with no waiting for completion.
> > >
> > > Fixes: 33bafe90824b ("tpm_tis: verify locality released before returning from release_locality")
> > > Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> > >
> > > ---
> > >
> > > v2: added fixes
> > > ---
> > >  drivers/char/tpm/tpm_tis_core.c | 47 +--------------------------------
> > >  1 file changed, 1 insertion(+), 46 deletions(-)
> > >
> > > diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> > > index f3ecde8df47d..431919d5f48a 100644
> > > --- a/drivers/char/tpm/tpm_tis_core.c
> > > +++ b/drivers/char/tpm/tpm_tis_core.c
> > > @@ -135,58 +135,13 @@ static bool check_locality(struct tpm_chip *chip, int l)
> > >  	return false;
> > >  }
> > >  
> > > -static bool locality_inactive(struct tpm_chip *chip, int l)
> > > -{
> > > -	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> > > -	int rc;
> > > -	u8 access;
> > > -
> > > -	rc = tpm_tis_read8(priv, TPM_ACCESS(l), &access);
> > > -	if (rc < 0)
> > > -		return false;
> > > -
> > > -	if ((access & (TPM_ACCESS_VALID | TPM_ACCESS_ACTIVE_LOCALITY))
> > > -	    == TPM_ACCESS_VALID)
> > > -		return true;
> > > -
> > > -	return false;
> > > -}
> > > -
> > >  static int release_locality(struct tpm_chip *chip, int l)
> > >  {
> > >  	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> > > -	unsigned long stop, timeout;
> > > -	long rc;
> > >  
> > >  	tpm_tis_write8(priv, TPM_ACCESS(l), TPM_ACCESS_ACTIVE_LOCALITY);
> > >  
> > > -	stop = jiffies + chip->timeout_a;
> > > -
> > > -	if (chip->flags & TPM_CHIP_FLAG_IRQ) {
> > > -again:
> > > -		timeout = stop - jiffies;
> > > -		if ((long)timeout <= 0)
> > > -			return -1;
> > > -
> > > -		rc = wait_event_interruptible_timeout(priv->int_queue,
> > > -						      (locality_inactive(chip, l)),
> > > -						      timeout);
> > > -
> > > -		if (rc > 0)
> > > -			return 0;
> > > -
> > > -		if (rc == -ERESTARTSYS && freezing(current)) {
> > > -			clear_thread_flag(TIF_SIGPENDING);
> > > -			goto again;
> > > -		}
> > > -	} else {
> > > -		do {
> > > -			if (locality_inactive(chip, l))
> > > -				return 0;
> > > -			tpm_msleep(TPM_TIMEOUT);
> > > -		} while (time_before(jiffies, stop));
> > > -	}
> > > -	return -1;
> > > +	return 0;
> > >  }
> > >  
> > >  static int request_locality(struct tpm_chip *chip, int l)
> > 
> > Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
> 
> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

Just noticed that the short summary is wrong: a fix is not a clean up.

Maybe "tpm_tis: Invoke locality release without wait" ? I'm also open
for other suggestions but the current is short summary does not describe
the patch.

/Jarkko