linux-kernel - Re: [PATCH v2 3/4] tee: add supp_nowait flag in tee

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Date:   Fri, 11 Jan 2019 13:00:49 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Daniel Thompson <daniel.thompson@...aro.org>
Cc:     linux-arm-kernel@...ts.infradead.org,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>, linux-kernel@...r.kernel.org,
        Jens Wiklander <jens.wiklander@...aro.org>, mpm@...enic.com,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Bhupesh Sharma <bhsharma@...hat.com>, tee-dev@...ts.linaro.org
Subject: Re: [PATCH v2 3/4] tee: add supp_nowait flag in tee_context struct

On Thu, 10 Jan 2019 at 19:53, Daniel Thompson
<daniel.thompson@...aro.org> wrote:
>
> On Thu, Jan 10, 2019 at 05:54:56PM +0530, Sumit Garg wrote:
> > This flag indicates that requests in this context should not wait for
> > tee-supplicant daemon to be started if not present and just return
> > with an error code. It is needed for requests which should be
> > non-blocking in nature like ones arising from TEE based kernel drivers
> > or any in kernel api that uses TEE internal client interface.
>
> This patch seems out of order in the patch set: Doesn't
> optee_enumarate_devices() require this feature if it is to
> work correctly with a TEE that does not implement the enumeate pTA.
>
> If so better to implement the feature first so that
> optee_emumerate_devices() works correctly when it first appears.
>

Agree, will make this patch as #2 in next version.

> >
> > Signed-off-by: Sumit Garg <sumit.garg@...aro.org>
> > ---
> >  drivers/tee/optee/supp.c | 10 +++++++++-
> >  drivers/tee/tee_core.c   |  2 ++
> >  include/linux/tee_drv.h  |  6 ++++++
> >  3 files changed, 17 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/tee/optee/supp.c b/drivers/tee/optee/supp.c
> > index 43626e1..92f56b8 100644
> > --- a/drivers/tee/optee/supp.c
> > +++ b/drivers/tee/optee/supp.c
> > @@ -88,10 +88,18 @@ u32 optee_supp_thrd_req(struct tee_context *ctx, u32 func, size_t num_params,
> >  {
> >       struct optee *optee = tee_get_drvdata(ctx->teedev);
> >       struct optee_supp *supp = &optee->supp;
> > -     struct optee_supp_req *req = kzalloc(sizeof(*req), GFP_KERNEL);
> > +     struct optee_supp_req *req;
> >       bool interruptable;
> >       u32 ret;
> >
> > +     /*
> > +      * Return in case there is no supplicant available and
> > +      * non-blocking request.
> > +      */
> > +     if (!supp->ctx && ctx->supp_nowait)
> > +             return TEEC_ERROR_COMMUNICATION;
> > +
> > +     req = kzalloc(sizeof(*req), GFP_KERNEL);
> >       if (!req)
> >               return TEEC_ERROR_OUT_OF_MEMORY;
> >
> > diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
> > index 9ddb89e..5d6c317 100644
> > --- a/drivers/tee/tee_core.c
> > +++ b/drivers/tee/tee_core.c
> > @@ -105,6 +105,7 @@ static int tee_open(struct inode *inode, struct file *filp)
> >       if (IS_ERR(ctx))
> >               return PTR_ERR(ctx);
> >
> > +     ctx->supp_nowait = false;
> >       filp->private_data = ctx;
> >       return 0;
> >  }
> > @@ -981,6 +982,7 @@ tee_client_open_context(struct tee_context *start,
> >       } while (IS_ERR(ctx) && PTR_ERR(ctx) != -ENOMEM);
> >
> >       put_device(put_dev);
> > +     ctx->supp_nowait = true;
>
> Why automatically set supp_nowait inside open_context() ?
>

I think this is the default behaviour (non-blocking request) that any
in kernel client would expect. Also this flag could be configured
again before call to open_session() if any in kernel client requires
different behaviour.

-Sumit

>
> >       return ctx;
> >  }
> >  EXPORT_SYMBOL_GPL(tee_client_open_context);
> > diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
> > index ed16bf1..fe1a920 100644
> > --- a/include/linux/tee_drv.h
> > +++ b/include/linux/tee_drv.h
> > @@ -49,6 +49,11 @@ struct tee_shm_pool;
> >   * @releasing:  flag that indicates if context is being released right now.
> >   *           It is needed to break circular dependency on context during
> >   *              shared memory release.
> > + * @supp_nowait: flag that indicates that requests in this context should not
> > + *              wait for tee-supplicant daemon to be started if not present
> > + *              and just return with an error code. It is needed for requests
> > + *              that arises from TEE based kernel drivers that should be
> > + *              non-blocking in nature.
> >   */
> >  struct tee_context {
> >       struct tee_device *teedev;
> > @@ -56,6 +61,7 @@ struct tee_context {
> >       void *data;
> >       struct kref refcount;
> >       bool releasing;
> > +     bool supp_nowait;
> >  };
> >
> >  struct tee_param_memref {
> > --
> > 2.7.4
> >