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References: <20230214152047.1143106-1-etienne.carriere@linaro.org> <Y+zG/t3zkN3p2pXG@jade>
In-Reply-To: <Y+zG/t3zkN3p2pXG@jade>
From:   Etienne Carriere <etienne.carriere@linaro.org>
Date:   Wed, 15 Feb 2023 17:03:16 +0100
Message-ID: <CAN5uoS_op00F-3CZKSh47BTP9YZxTjzrjpP9fJHbGEPHh3AaHg@mail.gmail.com>
Subject: Re: [PATCH v2 1/2] tee: system invocation
To:     Jens Wiklander <jens.wiklander@linaro.org>
Cc:     linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Sumit Garg <sumit.garg@linaro.org>,
        op-tee@lists.trustedfirmware.org,
        Cristian Marussi <cristian.marussi@arm.com>
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Precedence: bulk

Hi Jens,

On Wed, 15 Feb 2023 at 12:50, Jens Wiklander <jens.wiklander@linaro.org> wrote:
>
> 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?

A single Linux driver optee context (opened from
tee_client_open_context()) can be used for concurrent invocations of
TEE hence the implementation here supporting a linux context to
reserve several OP-TEE thread contexts.

> I wonder if keeping track on this shouldn't be done in a
> driver specific struct, perhaps struct optee_context_data for OP-TEE.

Yes, I can move that to optee private data since how TEE drivers
handle this are specific to their 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.

Ok.

Etienne

>
> 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
> >