Re: [PATCH] tpm_tis: work around status register bug in STMicroelectronics TPM

[Mimi Zohar <zohar@linux.ibm.com>]

On Tue, 2020-04-21 at 23:25 +0300, Jarkko Sakkinen wrote:
> On Tue, Apr 21, 2020 at 10:36:04AM -0400, Mimi Zohar wrote:
> > On Mon, 2020-04-20 at 15:28 -0700, James Bottomley wrote:
> > > On Mon, 2020-04-20 at 23:46 +0300, Jarkko Sakkinen wrote:
> > 
> > <snip>
> > 
> > > But more seriously: Nayna Jain did a series of patches improving the
> > > time it takes to poll the TPM for operations precisely because the TPM
> > > PCR extend was going so slowly:
> > > 
> > > https://lore.kernel.org/linux-integrity/20180516055125.5685-1-nayna@linux.vnet.ibm.com/
> > 
> > The original reason for us needing to improve the TPM performance was
> > due to the kernel scheduler change.  Refer to commit a233a0289cf9
> > ("tpm: msleep() delays - replace with usleep_range() in i2c nuvoton
> > driver").  That scheduler change prevented systems from booting.
> >  Bisecting the kernel to figure out the problem wasn't very
> > productive.
> > 
> > At least any TPM changes that affect the TPM performance really need
> > to take into account IMA requirements.
> 
> Thanks Mimi.
> 
> With my dynamic proposal it would work as it works now for system
> where it worked anyway, and would fix the systems where timeouts
> were too short.

Sure, but please remember this thread started out addressing an STM
TPM bug, not James' timeouts.  This part of the thread should be re-
named.

Mimi