linux-kernel - RE: [PATCH v2] tpm: add longer timeouts for creation commands.

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Date:   Tue, 6 Feb 2018 20:51:48 +0000
From:   "Winkler, Tomas" <tomas.winkler@...el.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
CC:     Jason Gunthorpe <jgg@...pe.ca>,
        "Usyskin, Alexander" <alexander.usyskin@...el.com>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] tpm: add longer timeouts for creation commands.

> 
> On Sun, Jan 28, 2018 at 10:17:39AM +0200, Tomas Winkler wrote:
> > TPM2_CC_Create(0x153) and TPM2_CC_CreatePrimary (0x131) involve
> > generation of crypto keys which can be a computationally intensive task.
> > The timeout is set to 3min.
> >
> > Signed-off-by: Tomas Winkler <tomas.winkler@...el.com>
> 
> This is still NAK because we need some kind of reference for the new value.
> Is that also right value for ARM64/TrustZone based TPMs?

The SPEC itself, doesn't define the timeout,  except for specific commands, 
also the current 'undefined' number is born in air, I wonder if you  can provide the reference as well.
If I would suggest to shorten the number that would maybe a problem for other implementation, 
but I don't see how the increase in timeout is adverse another implementations.
Key generation is computational intensive task because of generation of a prime number, so this is really 
dependent on device capabilities, so there is no better source of definition that HW itself.

Thanks
Tomas