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Subject: Re: [PATCH] tpm: Make timeout logic simpler and more robust
From:   Mimi Zohar <zohar@linux.ibm.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Calvin Owens <calvinowens@fb.com>
Cc:     Peter Huewe <peterhuewe@gmx.de>, Jason Gunthorpe <jgg@ziepe.ca>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-team@fb.com
Date:   Tue, 12 Mar 2019 12:56:37 -0400
In-Reply-To: <20190312123632.GB9243@linux.intel.com>
References: <358e89ed2b766d51b5f57abf31ab7a925ac63379.1552348123.git.calvinowens@fb.com>
         <20190312123632.GB9243@linux.intel.com>
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On Tue, 2019-03-12 at 14:36 +0200, Jarkko Sakkinen wrote:
> On Mon, Mar 11, 2019 at 04:54:04PM -0700, Calvin Owens wrote:
> > We're having lots of problems with TPM commands timing out, and we're
> > seeing these problems across lots of different hardware (both v1/v2).
> > 
> > I instrumented the driver to collect latency data, but I wasn't able to
> > find any specific timeout to fix: it seems like many of them are too
> > aggressive. So I tried replacing all the timeout logic with a single
> > universal long timeout, and found that makes our TPMs 100% reliable.
> > 
> > Given that this timeout logic is very complex, problematic, and appears
> > to serve no real purpose, I propose simply deleting all of it.
> > 
> > Signed-off-by: Calvin Owens <calvinowens@fb.com>
> 
> Have been thinking about this and I do agree. It has been like that
> before my times with this subsystem so when I did the original TPM2
> patches I carried this logic albeit even at that point I did not get it.
> Now that I've been maintaining for over three years I'm confident that
> this the Right Thing to do.

Please really consider this impact on IMA, before making this change.

Mimi