linux-kernel - [PATCH 1/2] tee: system invocation

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Message-Id: <20230130094157.1082712-1-etienne.carriere@linaro.org>
Date:   Mon, 30 Jan 2023 10:41:56 +0100
From:   Etienne Carriere <etienne.carriere@...aro.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org,
        Jens Wiklander <jens.wiklander@...aro.org>,
        Sumit Garg <sumit.garg@...aro.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Cristian Marussi <cristian.marussi@....com>,
        Etienne Carriere <etienne.carriere@...aro.org>
Subject: [PATCH 1/2] tee: system invocation

Adds TEE context flag sys_service to be enabled for invocation contexts
that should used TEE provisioned system resources. OP-TEE SMC ABI entry
rely this information to use a dedicated entry function to request
allocation of a system thread from a dedicated system context pool.

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 remove 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@...aro.org>
---
 drivers/tee/optee/optee_smc.h | 14 +++++++++++---
 drivers/tee/optee/smc_abi.c   |  6 +++++-
 include/linux/tee_drv.h       |  4 ++++
 3 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.h
index 73b5e7760d10..7c7eedf183c5 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 +431,9 @@ 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
+
 /*
  * 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..513038a138f6 100644
--- a/drivers/tee/optee/smc_abi.c
+++ b/drivers/tee/optee/smc_abi.c
@@ -889,7 +889,11 @@ 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->sys_service &&
+		    (optee->smc.sec_caps & OPTEE_SMC_SEC_CAP_SYSTEM_THREAD))
+			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 {
diff --git a/include/linux/tee_drv.h b/include/linux/tee_drv.h
index 17eb1c5205d3..1ff292ba7679 100644
--- a/include/linux/tee_drv.h
+++ b/include/linux/tee_drv.h
@@ -47,6 +47,9 @@ 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.
+ * @sys_service: flag set by the TEE Client to indicate that it is part of
+ *		 a system service and that the TEE may use resources reserved
+ *		 for this.
  */
 struct tee_context {
 	struct tee_device *teedev;
@@ -55,6 +58,7 @@ struct tee_context {
 	bool releasing;
 	bool supp_nowait;
 	bool cap_memref_null;
+	bool sys_service;
 };
 
 struct tee_param_memref {
-- 
2.25.1