linux-kernel - Re: [PATCH v5 2/4] tee: add supp_nowait flag in tee

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Date:   Thu, 24 Jan 2019 09:48:07 +0000
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Sumit Garg <sumit.garg@...aro.org>
Cc:     jens.wiklander@...aro.org, herbert@...dor.apana.org.au,
        ard.biesheuvel@...aro.org, linux-arm-kernel@...ts.infradead.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        yamada.masahiro@...ionext.com, michal.lkml@...kovi.net,
        mpm@...enic.com, robh+dt@...nel.org, mark.rutland@....com,
        arnd@...db.de, gregkh@...uxfoundation.org, bhsharma@...hat.com,
        tee-dev@...ts.linaro.org
Subject: Re: [PATCH v5 2/4] tee: add supp_nowait flag in tee_context struct

On Thu, Jan 24, 2019 at 11:24:37AM +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.
> 
> Signed-off-by: Sumit Garg <sumit.garg@...aro.org>

Reviewed-by: Daniel Thompson <daniel.thompson@...aro.org>

> ---
>  drivers/tee/optee/supp.c | 10 +++++++++-
>  drivers/tee/tee_core.c   | 13 +++++++++++++
>  include/linux/tee_drv.h  |  6 ++++++
>  3 files changed, 28 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 9f4c8bc..2612dfa 100644
> --- a/drivers/tee/tee_core.c
> +++ b/drivers/tee/tee_core.c
> @@ -105,6 +105,11 @@ static int tee_open(struct inode *inode, struct file *filp)
>  	if (IS_ERR(ctx))
>  		return PTR_ERR(ctx);
>  
> +	/*
> +	 * Default user-space behaviour is to wait for tee-supplicant
> +	 * if not present for any requests in this context.
> +	 */
> +	ctx->supp_nowait = false;
>  	filp->private_data = ctx;
>  	return 0;
>  }
> @@ -981,6 +986,14 @@ tee_client_open_context(struct tee_context *start,
>  	} while (IS_ERR(ctx) && PTR_ERR(ctx) != -ENOMEM);
>  
>  	put_device(put_dev);
> +	/*
> +	 * Default behaviour for in kernel client is to not wait for
> +	 * tee-supplicant if not present for any requests in this context.
> +	 * Also this flag could be configured again before call to
> +	 * tee_client_open_session() if any in kernel client requires
> +	 * different behaviour.
> +	 */
> +	ctx->supp_nowait = true;
>  	return ctx;
>  }
>  EXPORT_SYMBOL_GPL(tee_client_open_context);
> diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
> index ce957ce..56d7f1b 100644
> --- a/include/linux/tee_drv.h
> +++ b/include/linux/tee_drv.h
> @@ -50,6 +50,11 @@ 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;
> @@ -57,6 +62,7 @@ struct tee_context {
>  	void *data;
>  	struct kref refcount;
>  	bool releasing;
> +	bool supp_nowait;
>  };
>  
>  struct tee_param_memref {
> -- 
> 2.7.4
>