linux-kernel - Re: [PATCH] tpm: sleep at least <...> ms in tpm

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Date:   Mon, 16 May 2022 20:54:12 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Mimi Zohar <zohar@...ux.ibm.com>
Cc:     Johannes Holland <johannes.holland@...ineon.com>,
        Nayna <nayna@...ux.vnet.ibm.com>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        peterhuewe@....de, jgg@...pe.ca
Subject: Re: [PATCH] tpm: sleep at least <...> ms in tpm_msleep()

On Thu, May 12, 2022 at 08:21:17AM -0400, Mimi Zohar wrote:
> On Wed, 2022-05-11 at 18:16 +0300, Jarkko Sakkinen wrote:
> > On Tue, May 10, 2022 at 01:29:03PM +0200, Johannes Holland wrote:
> > > To comply with protocol requirements, minimum polling times must often
> > > be adhered to. Therefore, a macro like tpm_msleep() should sleep at
> > > least the given amount of time (not up to the given period). Have
> > > tpm_msleep() sleep at least the given number of milliseconds.
> > > 
> > > Signed-off-by: Johannes Holland <johannes.holland@...ineon.com>
> > > ---
> > >  drivers/char/tpm/tpm.h | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> > > index 2163c6ee0d36..0971b55fffe3 100644
> > > --- a/drivers/char/tpm/tpm.h
> > > +++ b/drivers/char/tpm/tpm.h
> > > @@ -185,8 +185,8 @@ int tpm_pm_resume(struct device *dev);
> > >  
> > >  static inline void tpm_msleep(unsigned int delay_msec)
> > >  {
> > > -	usleep_range((delay_msec * 1000) - TPM_TIMEOUT_RANGE_US,
> > > -		     delay_msec * 1000);
> > > +	usleep_range(delay_msec * 1000, (delay_msec * 1000)
> > > +		     + TPM_TIMEOUT_RANGE_US);
> > >  };
> > >  
> > >  int tpm_chip_start(struct tpm_chip *chip);
> > > -- 
> > > 2.34.1
> > > 
> > 
> > For this I would really like to hear a 2nd opinion from Nayna and Mimi.
> 
> This patch reverts commit 5ef924d9e2e8 ("tpm: use tpm_msleep() value as
> max delay").    Are you experiencing TPM issues that require it?
> 
> thanks,
> 
> Mimi

Yeah, there's no data to support making anything.  Without a live
system having issues with this, I guess this quite definitive NAK.

BR, Jarkko