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Date: Mon, 18 Jun 2018 21:26:11 +0300
From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Tadeusz Struk <tadeusz.struk@intel.com>
Cc: flihp <flihp@twobit.us>, linux-integrity@vger.kernel.org
Subject: Re: [PATCH] tpm: add support for nonblocking operation
Message-ID: <20180618182611.GG20697@linux.intel.com>
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On Mon, Jun 11, 2018 at 05:13:34PM -0700, Tadeusz Struk wrote:
> On 06/08/2018 12:36 PM, flihp wrote:
> > On 06/04/2018 12:55 PM, Jarkko Sakkinen wrote:
> >> On Thu, May 31, 2018 at 04:29:09PM -0700, Tadeusz Struk wrote:
> >>> The TCG SAPI specification [1] defines a set of functions, which allows
> >>> applications to use the TPM device in either blocking or non-blocking fashion.
> >>> Each command defined by the specification has a corresponding
> >>> Tss2_Sys_<COMMAND>_Prepare() and Tss2_Sys_<COMMAND>_Complete() call, which
> >>> together with Tss2_Sys_ExecuteAsync() is designed to allow asynchronous
> >>> mode of operation. Currently the driver supports only blocking calls, which
> >>> doesn't allow asynchronous operation. This patch changes it and adds support
> >>> for nonblocking write and a new poll function to enable applications using
> >>> the API as designed by the spec.
> >>> The new functionality can be tested using standard TPM tools implemented
> >>> in [2], with modified TCTI from [3].
> >>
> >> I would need some statistics before I have interest to take these
> >> changes in any form eg use case where this matters in the end.
> > 
> > The use cases motivating this feature are the same ones that motivated
> > the non-blocking behavior of other kernel interfaces (files, sockets and
> > other hardware) that has the potential to block threads in a process. By
> > implementing this same behavior in the TPM driver our goal is to enable
> > use of the TPM in programming languages / frameworks implementing an
> > "event-driven" model. There are a lot of them out there but since the
> > TSS2 APIs are currently limited to C our example code is in glib / GSource.
> > 
> > Hopefully this is sufficient but if it isn't it would help us to get
> > additional details on what you're looking for.
> 
> I tried to run some tests w/r/t blocking to non-blocking.
> and for example for tpm2_createprimary (type RSA) it looks more less like this:
> blocking:
> real	0m3.194s
> user	0m0.052s
> sys	0m0.094s
> 
> vs nonblocking:
> real	0m1.031s
> user	0m0.043s
> sys	0m0.162s
> 
> that's on Minnowboard Turbot D0 PLATFORM
> running FW Version: MNW2MAX1.X64.0097.R01.1709211204
> 
> The number are different every time I run it though.
> Is this what you wanted to see?

Thanks, this and Philips explanation make it worth of looking into!

/Jarkko