linux-kernel - Re: [PATCH v6 0/4] Introduce TEE bus driver framework

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Message-ID: <CAFA6WYNbLMOdR6mQSC=ywS0EpfCTSGQ16Qr_xBc13AzW_d-FGA@mail.gmail.com>
Date:   Tue, 12 Feb 2019 18:25:11 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Jens Wiklander <jens.wiklander@...aro.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Matt Mackall <mpm@...enic.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Bhupesh Sharma <bhsharma@...hat.com>, tee-dev@...ts.linaro.org
Subject: Re: [PATCH v6 0/4] Introduce TEE bus driver framework

On Tue, 12 Feb 2019 at 17:41, Ard Biesheuvel <ard.biesheuvel@...aro.org> wrote:
>
> On Tue, 12 Feb 2019 at 13:09, Sumit Garg <sumit.garg@...aro.org> wrote:
> >
> > On Tue, 12 Feb 2019 at 16:35, Ard Biesheuvel <ard.biesheuvel@...aro.org> wrote:
> > >
> > > On Tue, 29 Jan 2019 at 06:50, Sumit Garg <sumit.garg@...aro.org> wrote:
> > > >
> > > > This series introduces a generic TEE bus driver concept for TEE based
> > > > kernel drivers which would like to communicate with TEE based devices/
> > > > services.
> > > >
> > > > Patch #1 adds TEE bus concept where devices/services are identified via
> > > > Universally Unique Identifier (UUID) and drivers register a table of
> > > > device UUIDs which they can support. This concept also allows for device
> > > > enumeration to be specific to corresponding TEE implementation like
> > > > OP-TEE etc.
> > > >
> > > > Patch #2 adds supp_nowait flag for non-blocking requests arising via
> > > > TEE internal client interface.
> > > >
> > > > Patch #3 adds TEE bus device enumeration support for OP-TEE. OP-TEE
> > > > provides a pseudo TA to enumerate TAs which can act as devices/services
> > > > for TEE bus.
> > > >
> > > > Patch #4 adds OP-TEE based hwrng driver which act as TEE bus driver.
> > > > On ARM SoC's with TrustZone enabled, peripherals like entropy sources
> > > > might not be accessible to normal world (linux in this case) and rather
> > > > accessible to secure world (OP-TEE in this case) only. So this driver
> > > > aims to provides a generic interface to OP-TEE based random number
> > > > generator service.
> > > >
> > > > Example case is Developerbox based on Socionext's Synquacer SoC [1]
> > > > which provides 7 thermal sensors accessible from secure world only which
> > > > could be used as entropy sources (thermal/measurement noise).
> > > >
> > > > [1] https://www.96boards.org/product/developerbox/
> > > >
> > > > Changes in v6:
> > > >
> > > > 1. Incorporate some nitpicks in patch #1 and #3.
> > > > 2. Bundle all statics in a data structure in patch #4 and use dev_*
> > > >    instead of pr_*.
> > > > 3. Add reviewed-by tags for patch #1, #2 and #3.
> > > >
> > > > Changes in v5:
> > > >
> > > > 1. Add support in module device table for TEE bus devices.
> > > > 2. Correct license for optee-rng module.
> > > >
> > > > Changes in v4:
> > > >
> > > > 1. Use typedef instead of single member tee_client_device_id struct.
> > > > 2. Incorporate TEE bus nitpicks.
> > > >
> > > > Changes in v3:
> > > >
> > > > 1. Fixed bus error path in Patch #1.
> > > > 2. Reversed order of Patch #2 and #3.
> > > > 3. Fixed miscellaneous syntax comments and memory leak.
> > > > 4. Added comments in Patch #2 for supp_nowait flag.
> > > >
> > > > Changes in v2:
> > > >
> > > > Based on review comments, the scope of this series has increased as
> > > > follows:
> > > >
> > > > 1. Added TEE bus driver framework.
> > > > 2. Added OP-TEE based device enumeration.
> > > > 3. Register optee-rng driver as TEE bus driver.
> > > > 4. Removed DT dependency for optee-rng device UUID.
> > > > 5. Added supp_nowait flag.
> > > >
> > > > Sumit Garg (4):
> > > >   tee: add bus driver framework for TEE based devices
> > > >   tee: add supp_nowait flag in tee_context struct
> > > >   tee: optee: add TEE bus device enumeration support
> > > >   hwrng: add OP-TEE based rng driver
> > > >
> > >
> > > For this series
> > >
> > > Tested-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> > >
> >
> > Thanks. BTW, Jens has created a GIT PULL[1] to incorporate this patch-set.
> >
> > > although I had to load optee.ko manually in order for the udev
> > > autoload of optee_rng to trigger.
> >
> > Did you built OP-TEE module as out-of-tree? OP-TEE by-default is
> > built-in kernel module as per following configs in default defconfig:
> >
> > CONFIG_TEE=y
> > CONFIG_OPTEE=y
> >
>
> Yes, but the distros will carry it as a module.
>

Hmm, I see. So in this case OP-TEE module needs to be loaded manually
due to missing modalias for udev autoload.

-Sumit

> > > Not sure where the discussion went
> > > last time, but could we please add "linaro,optee-tz" as a DT modalias
> > > to the optee.ko module in any case?
> > >
> >
> > This change is already part of your RFC patch [2] and I agree to make
> > OP-TEE as platform driver.
> >
> > [1] https://lkml.org/lkml/2019/2/4/104
> > [2] https://lkml.org/lkml/2018/12/27/196
> >
>
> Indeed, but iirc there was a question from Jens and I wasn't sure it
> had been answered in the mean time.