linux-kernel - Re: [PATCH] tpm: Make timeout logic simpler and more robust

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Message-Id: <1552415520.24794.87.camel@linux.ibm.com>
Date:   Tue, 12 Mar 2019 14:32:00 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     James Bottomley <James.Bottomley@...senPartnership.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Peter Hüwe <PeterHuewe@....de>
Cc:     Calvin Owens <calvinowens@...com>, Jason Gunthorpe <jgg@...pe.ca>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH] tpm: Make timeout logic simpler and more robust

On Tue, 2019-03-12 at 10:14 -0700, James Bottomley wrote:

> > > However, I am saying we should root cause this problem rather than
> > > take a blind shot at the apparent timeout complexity.  My timeout
> > > instability is definitely related to the polling adjustments, so
> > > it's not unreasonable to think Facebooks might be as well.
> > 
> > James, I thought Peter sent you a tis "debug" tool to help you debug
> > the problem you're seeing.  Whatever happened?

https://patchwork.kernel.org/patch/10520247/#22107607

> 
> No, not seen one.  I have tried to debug the problem, but it's really
> odd: my TPM is a polled nuvoton (so no irq line).  If you poll the data
> ready bit on my TPM too often, it simply drops off the bus and every
> TPM operation after that times out.  The only way to recover is to
> reboot.
> 
> James
>