Re: [PATCH v2 1/2] tee: system invocation

[Jens Wiklander <jens.wiklander@linaro.org>]

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On Tue, Feb 14, 2023 at 04:20:46PM +0100, Etienne Carriere wrote:
> Adds TEE system invocation context provisioning for a Linux driver
> to provision execution contexts for invocation of system service
> hosted in TEE. OP-TEE SMC ABI implements such invocation context
> provisioning.
> 
> This feature is needed when a TEE invocation cannot afford to wait for
> a free TEE thread when all TEE threads context are used and suspended
> as these may be suspended waiting for a system service, as an SCMI clock
> or voltage regulator, to be enabled. An example is when OP-TEE invokes
> a Linux OS remote service (RPC) to access an eMMC RPMB partition and
> the eMMC device is supplied by an OP-TEE SCMI regulator.
> 
> Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
> ---
> Change since v1
> - Addressed comment on Linux client to claim reservation on TEE context.
>   This brings 2 new operations from client to TEE to request and release
>   system thread contexts: 2 new tee_drv.h API functions, 2 new ops
>   functions in struct tee_driver_ops. The OP-TEE implement shall implement
>   2 new fastcall SMC funcIDs.
> - Fixed typos in commit message.
> ---
>  drivers/tee/optee/optee_smc.h | 60 +++++++++++++++++++++++++++++++++--
>  drivers/tee/optee/smc_abi.c   | 34 +++++++++++++++++++-
>  drivers/tee/tee_core.c        | 30 ++++++++++++++++++
>  include/linux/tee_drv.h       | 21 ++++++++++++
>  4 files changed, 141 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.h
> index 73b5e7760d10..75b19e1bd185 100644
> --- a/drivers/tee/optee/optee_smc.h
> +++ b/drivers/tee/optee/optee_smc.h
> @@ -108,7 +108,8 @@ struct optee_smc_call_get_os_revision_result {
>   * Call with struct optee_msg_arg as argument
>   *
>   * When called with OPTEE_SMC_CALL_WITH_RPC_ARG or
> - * OPTEE_SMC_CALL_WITH_REGD_ARG in a0 there is one RPC struct optee_msg_arg
> + * OPTEE_SMC_CALL_WITH_REGD_ARG or OPTEE_SMC_FUNCID_CALL_SYSTEM_WITH_REGD_ARG
> + * in a0 there is one RPC struct optee_msg_arg
>   * following after the first struct optee_msg_arg. The RPC struct
>   * optee_msg_arg has reserved space for the number of RPC parameters as
>   * returned by OPTEE_SMC_EXCHANGE_CAPABILITIES.
> @@ -130,8 +131,8 @@ struct optee_smc_call_get_os_revision_result {
>   * a4-6	Not used
>   * a7	Hypervisor Client ID register
>   *
> - * Call register usage, OPTEE_SMC_CALL_WITH_REGD_ARG:
> - * a0	SMC Function ID, OPTEE_SMC_CALL_WITH_REGD_ARG
> + * Call register usage, OPTEE_SMC_CALL_WITH_REGD_ARG and OPTEE_SMC_FUNCID_CALL_SYSTEM_WITH_REGD_ARG:
> + * a0	SMC Function ID, OPTEE_SMC_CALL_WITH_REGD_ARG or OPTEE_SMC_FUNCID_CALL_SYSTEM_WITH_REGD_ARG
>   * a1	Upper 32 bits of a 64-bit shared memory cookie
>   * a2	Lower 32 bits of a 64-bit shared memory cookie
>   * a3	Offset of the struct optee_msg_arg in the shared memory with the
> @@ -175,6 +176,8 @@ struct optee_smc_call_get_os_revision_result {
>  	OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_WITH_RPC_ARG)
>  #define OPTEE_SMC_CALL_WITH_REGD_ARG \
>  	OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_WITH_REGD_ARG)
> +#define OPTEE_SMC_CALL_SYSTEM_WITH_REGD_ARG \
> +	OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_SYSTEM_WITH_REGD_ARG)
>  
>  /*
>   * Get Shared Memory Config
> @@ -254,6 +257,8 @@ struct optee_smc_get_shm_config_result {
>  #define OPTEE_SMC_SEC_CAP_ASYNC_NOTIF		BIT(5)
>  /* Secure world supports pre-allocating RPC arg struct */
>  #define OPTEE_SMC_SEC_CAP_RPC_ARG		BIT(6)
> +/* Secure world provisions thread for system service invocation */
> +#define OPTEE_SMC_SEC_CAP_SYSTEM_THREAD		BIT(7)
>  
>  #define OPTEE_SMC_FUNCID_EXCHANGE_CAPABILITIES	9
>  #define OPTEE_SMC_EXCHANGE_CAPABILITIES \
> @@ -426,6 +431,55 @@ struct optee_smc_disable_shm_cache_result {
>  /* See OPTEE_SMC_CALL_WITH_REGD_ARG above */
>  #define OPTEE_SMC_FUNCID_CALL_WITH_REGD_ARG	19
>  
> +/* See OPTEE_SMC_CALL_SYSTEM_WITH_REGD_ARG above */
> +#define OPTEE_SMC_FUNCID_CALL_SYSTEM_WITH_REGD_ARG	20
> +
> +/*
> + * Request reservation of a system invocation thread context in OP-TEE
> + *
> + * Call register usage:
> + * a0	SMC Function ID: OPTEE_SMC_CALL_RESERVE_SYS_THREAD
> + * a1-6	Not used
> + * a7	Hypervisor Client ID register
> + *
> + * Normal return register usage:
> + * a0	Return value, OPTEE_SMC_RETURN_*
> + * a1-3	Not used
> + * a4-7	Preserved
> + *
> + * Possible return values:
> + * OPTEE_SMC_RETURN_UNKNOWN_FUNCTION	Trusted OS does not recognize this
> + *                                      function.
> + * OPTEE_SMC_RETURN_OK			Call successfully completed.
> + * OPTEE_SMC_RETURN_ETHREAD_LIMIT	Number of Trusted OS threads exceeded
> + *                                      for the request.
> + */
> +#define OPTEE_SMC_FUNCID_CALL_RESERVE_SYS_THREAD	21
> +#define OPTEE_SMC_CALL_RESERVE_SYS_THREAD \
> +	OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_RESERVE_SYS_THREAD)
> +
> +/*
> + * Unregister reservation of a system invocation thread context in OP-TEE
> + *
> + * Call register usage:
> + * a0	SMC Function ID: OPTEE_SMC_CALL_UNRESERVE_SYS_THREAD
> + * a1-6	Not used
> + * a7	Hypervisor Client ID register
> + *
> + * Normal return register usage:
> + * a0	Return value, OPTEE_SMC_RETURN_*
> + * a1-3	Not used
> + * a4-7	Preserved
> + *
> + * Possible return values:
> + * OPTEE_SMC_RETURN_UNKNOWN_FUNCTION	Trusted OS does not recognize this
> + *                                      function.
> + * OPTEE_SMC_RETURN_OK			Call successfully completed.
> + */
> +#define OPTEE_SMC_FUNCID_CALL_UNRESERVE_SYS_THREAD	22
> +#define OPTEE_SMC_CALL_UNRESERVE_SYS_THREAD \
> +	OPTEE_SMC_STD_CALL_VAL(OPTEE_SMC_FUNCID_CALL_UNRESERVE_SYS_THREAD)
> +
>  /*
>   * Resume from RPC (for example after processing a foreign interrupt)
>   *
> diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c
> index a1c1fa1a9c28..013b5ae31c0e 100644
> --- a/drivers/tee/optee/smc_abi.c
> +++ b/drivers/tee/optee/smc_abi.c
> @@ -889,7 +889,10 @@ static int optee_smc_do_call_with_arg(struct tee_context *ctx,
>  	}
>  
>  	if  (rpc_arg && tee_shm_is_dynamic(shm)) {
> -		param.a0 = OPTEE_SMC_CALL_WITH_REGD_ARG;
> +		if (ctx->system_ctx_count)
> +			param.a0 = OPTEE_SMC_CALL_SYSTEM_WITH_REGD_ARG;
> +		else
> +			param.a0 = OPTEE_SMC_CALL_WITH_REGD_ARG;
>  		reg_pair_from_64(&param.a1, &param.a2, (u_long)shm);
>  		param.a3 = offs;
>  	} else {
> @@ -1085,6 +1088,33 @@ static int optee_smc_open(struct tee_context *ctx)
>  	return optee_open(ctx, sec_caps & OPTEE_SMC_SEC_CAP_MEMREF_NULL);
>  }
>  
> +static int optee_request_sys_ctx(struct tee_context *ctx)
> +{
> +	struct optee *optee = tee_get_drvdata(ctx->teedev);
> +	struct arm_smccc_res res;
> +
> +	if (!(optee->smc.sec_caps & OPTEE_SMC_SEC_CAP_SYSTEM_THREAD))
> +		return -EINVAL;
> +
> +	optee->smc.invoke_fn(OPTEE_SMC_CALL_RESERVE_SYS_THREAD,
> +			     0, 0, 0, 0, 0, 0, 0, &res);
> +
> +	if (res.a0 != OPTEE_SMC_RETURN_OK)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
> +static void optee_release_sys_ctx(struct tee_context *ctx)
> +{
> +	struct optee *optee = tee_get_drvdata(ctx->teedev);
> +	struct arm_smccc_res res;
> +
> +	if (optee->smc.sec_caps & OPTEE_SMC_SEC_CAP_SYSTEM_THREAD)
> +		optee->smc.invoke_fn(OPTEE_SMC_CALL_UNRESERVE_SYS_THREAD,
> +				     0, 0, 0, 0, 0, 0, 0, &res);
> +}
> +
>  static const struct tee_driver_ops optee_clnt_ops = {
>  	.get_version = optee_get_version,
>  	.open = optee_smc_open,
> @@ -1095,6 +1125,8 @@ static const struct tee_driver_ops optee_clnt_ops = {
>  	.cancel_req = optee_cancel_req,
>  	.shm_register = optee_shm_register,
>  	.shm_unregister = optee_shm_unregister,
> +	.system_ctx_request = optee_request_sys_ctx,
> +	.system_ctx_release = optee_release_sys_ctx,
>  };
>  
>  static const struct tee_desc optee_clnt_desc = {
> diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
> index 98da206cd761..a7dfdea5d85b 100644
> --- a/drivers/tee/tee_core.c
> +++ b/drivers/tee/tee_core.c
> @@ -5,6 +5,7 @@
>  
>  #define pr_fmt(fmt) "%s: " fmt, __func__
>  
> +#include <linux/bug.h>
>  #include <linux/cdev.h>
>  #include <linux/cred.h>
>  #include <linux/fs.h>
> @@ -1141,10 +1142,39 @@ EXPORT_SYMBOL_GPL(tee_client_open_context);
>  
>  void tee_client_close_context(struct tee_context *ctx)
>  {
> +	while (ctx->system_ctx_count)
> +		tee_client_release_system_context(ctx);
> +
>  	teedev_close_context(ctx);
>  }
>  EXPORT_SYMBOL_GPL(tee_client_close_context);
>  
> +int tee_client_request_system_context(struct tee_context *ctx)
> +{
> +	int ret;
> +
> +	if (!ctx->teedev->desc->ops->system_ctx_request ||
> +	    !ctx->teedev->desc->ops->system_ctx_release)
> +		return -EINVAL;
> +
> +	ret = ctx->teedev->desc->ops->system_ctx_request(ctx);
> +	if (!ret)
> +		ctx->system_ctx_count++;
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(tee_client_request_system_context);
> +
> +void tee_client_release_system_context(struct tee_context *ctx)
> +{
> +	if (ctx->system_ctx_count &&
> +	    ctx->teedev->desc->ops->system_ctx_release) {
> +		ctx->teedev->desc->ops->system_ctx_release(ctx);
> +		ctx->system_ctx_count--;
> +	}
> +}
> +EXPORT_SYMBOL_GPL(tee_client_release_system_context);
> +
>  void tee_client_get_version(struct tee_context *ctx,
>  			    struct tee_ioctl_version_data *vers)
>  {
> diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
> index 17eb1c5205d3..45577256bb71 100644
> --- a/include/linux/tee_drv.h
> +++ b/include/linux/tee_drv.h
> @@ -47,6 +47,8 @@ struct tee_shm_pool;
>   *              non-blocking in nature.
>   * @cap_memref_null: flag indicating if the TEE Client support shared
>   *                   memory buffer with a NULL pointer.
> + * @system_ctx_count: Number of system invocation contexts provisioned for
> + *                    this TEE client or 0.
>   */
>  struct tee_context {
>  	struct tee_device *teedev;
> @@ -55,6 +57,7 @@ struct tee_context {
>  	bool releasing;
>  	bool supp_nowait;
>  	bool cap_memref_null;
> +	unsigned int system_ctx_count;

Does it make sense for a tee_context to reserve more than one system
context/thread? I wonder if keeping track on this shouldn't be done in a
driver specific struct, perhaps struct optee_context_data for OP-TEE.

>  };
>  
>  struct tee_param_memref {
> @@ -90,6 +93,8 @@ struct tee_param {
>   * @supp_send:		called for supplicant to send a response
>   * @shm_register:	register shared memory buffer in TEE
>   * @shm_unregister:	unregister shared memory buffer in TEE
> + * @system_ctx_request:	Request provisioning of a new system context in TEE
> + * @system_ctx_release:	Release a provisioned system context in TEE
>   */
>  struct tee_driver_ops {
>  	void (*get_version)(struct tee_device *teedev,
> @@ -112,6 +117,8 @@ struct tee_driver_ops {
>  			    struct page **pages, size_t num_pages,
>  			    unsigned long start);
>  	int (*shm_unregister)(struct tee_context *ctx, struct tee_shm *shm);
> +	int (*system_ctx_request)(struct tee_context *ctx);
> +	void (*system_ctx_release)(struct tee_context *ctx);
>  };
>  
>  /**
> @@ -397,6 +404,20 @@ tee_client_open_context(struct tee_context *start,
>   */
>  void tee_client_close_context(struct tee_context *ctx);
>  
> +/**
> + * tee_client_request_system_context() - Close a TEE context

Copy & paste error

> + * @ctx:	TEE context to close
> + *
> + * @return 0 on success else an error code
> + */
> +int tee_client_request_system_context(struct tee_context *ctx);
> +
> +/**
> + * tee_client_release_system_context() - Release a reserved system exec context

Please drop "exec", it's not mentioned anywhere else.

Thanks,
Jens

> + * @ctx:	TEE context reference
> + */
> +void tee_client_release_system_context(struct tee_context *ctx);
> +
>  /**
>   * tee_client_get_version() - Query version of TEE
>   * @ctx:	TEE context to TEE to query
> -- 
> 2.25.1
>