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

Hi Jens,

On Wed, 15 Feb 2023 at 12:50, Jens Wiklander [off-list ref] wrote:

On Tue, Feb 14, 2023 at 04:20:46PM +0100, Etienne Carriere wrote:

quoted

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 <redacted>
---
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.

quoted

 };

 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

quoted

+ * @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

quoted

+ * @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

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