tee: optee: support tracking system threads

Adds support in the OP-TEE driver to keep track of reserved system
threads. The logic allows one OP-TEE thread to be reserved to TEE system
sessions.

The optee_cq_*() functions are updated to handle this if enabled,
that is when TEE describes how many thread context it supports
and when at least 1 session has registered as a system session
(using tee_client_system_session()).

For sake of simplicity, initialization of call queue management
is factorized into new helper function optee_cq_init().

The SMC ABI part of the driver enables this tracking, but the
FF-A ABI part does not.

Co-developed-by: Jens Wiklander <jens.wiklander@linaro.org>
Co-developed-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Signed-off-by: Etienne Carriere <etienne.carriere@foss.st.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

drivers/tee/optee/call.c

@@ -39,9 +39,29 @@ struct optee_shm_arg_entry {
 	DECLARE_BITMAP(map, MAX_ARG_COUNT_PER_ENTRY);
 };
 
+void optee_cq_init(struct optee_call_queue *cq, int thread_count)
+{
+	mutex_init(&cq->mutex);
+	INIT_LIST_HEAD(&cq->waiters);
+
+	/*
+	 * If cq->total_thread_count is 0 then we're not trying to keep
+	 * track of how many free threads we have, instead we're relying on
+	 * the secure world to tell us when we're out of thread and have to
+	 * wait for another thread to become available.
+	 */
+	cq->total_thread_count = thread_count;
+	cq->free_thread_count = thread_count;
+}
+
 void optee_cq_wait_init(struct optee_call_queue *cq,
 			struct optee_call_waiter *w, bool sys_thread)
 {
+	unsigned int free_thread_threshold;
+	bool need_wait = false;
+
+	memset(w, 0, sizeof(*w));
+
 	/*
 	 * We're preparing to make a call to secure world. In case we can't
 	 * allocate a thread in secure world we'll end up waiting in
@@ -60,8 +80,38 @@ void optee_cq_wait_init(struct optee_call_queue *cq,
 	 */
 	init_completion(&w->c);
 	list_add_tail(&w->list_node, &cq->waiters);
+	w->sys_thread = sys_thread;
+
+	if (cq->total_thread_count) {
+		if (sys_thread || !cq->sys_thread_req_count)
+			free_thread_threshold = 0;
+		else
+			free_thread_threshold = 1;
+
+		if (cq->free_thread_count > free_thread_threshold)
+			cq->free_thread_count--;
+		else
+			need_wait = true;
+	}
 
 	mutex_unlock(&cq->mutex);
+
+	while (need_wait) {
+		optee_cq_wait_for_completion(cq, w);
+		mutex_lock(&cq->mutex);
+
+		if (sys_thread || !cq->sys_thread_req_count)
+			free_thread_threshold = 0;
+		else
+			free_thread_threshold = 1;
+
+		if (cq->free_thread_count > free_thread_threshold) {
+			cq->free_thread_count--;
+			need_wait = false;
+		}
+
+		mutex_unlock(&cq->mutex);
+	}
 }
 
 void optee_cq_wait_for_completion(struct optee_call_queue *cq,
@@ -83,6 +133,14 @@ static void optee_cq_complete_one(struct optee_call_queue *cq)
 {
 	struct optee_call_waiter *w;
 
+	/* Wake a waiting system session if any, prior to a normal session */
+	list_for_each_entry(w, &cq->waiters, list_node) {
+		if (w->sys_thread && !completion_done(&w->c)) {
+			complete(&w->c);
+			return;
+		}
+	}
+
 	list_for_each_entry(w, &cq->waiters, list_node) {
 		if (!completion_done(&w->c)) {
 			complete(&w->c);
@@ -104,6 +162,8 @@ void optee_cq_wait_final(struct optee_call_queue *cq,
 	/* Get out of the list */
 	list_del(&w->list_node);
 
+	cq->free_thread_count++;
+
 	/* Wake up one eventual waiting task */
 	optee_cq_complete_one(cq);
 
@@ -119,6 +179,28 @@ void optee_cq_wait_final(struct optee_call_queue *cq,
 	mutex_unlock(&cq->mutex);
 }
 
+/* Count registered system sessions to reserved a system thread or not */
+static bool optee_cq_incr_sys_thread_count(struct optee_call_queue *cq)
+{
+	if (cq->total_thread_count <= 1)
+		return false;
+
+	mutex_lock(&cq->mutex);
+	cq->sys_thread_req_count++;
+	mutex_unlock(&cq->mutex);
+
+	return true;
+}
+
+static void optee_cq_decr_sys_thread_count(struct optee_call_queue *cq)
+{
+	mutex_lock(&cq->mutex);
+	cq->sys_thread_req_count--;
+	/* If there's someone waiting, let it resume */
+	optee_cq_complete_one(cq);
+	mutex_unlock(&cq->mutex);
+}
+
 /* Requires the filpstate mutex to be held */
 static struct optee_session *find_session(struct optee_context_data *ctxdata,
 					  u32 session_id)
@@ -361,6 +443,27 @@ out:
 	return rc;
 }
 
+int optee_system_session(struct tee_context *ctx, u32 session)
+{
+	struct optee *optee = tee_get_drvdata(ctx->teedev);
+	struct optee_context_data *ctxdata = ctx->data;
+	struct optee_session *sess;
+	int rc = -EINVAL;
+
+	mutex_lock(&ctxdata->mutex);
+
+	sess = find_session(ctxdata, session);
+	if (sess && (sess->use_sys_thread ||
+		     optee_cq_incr_sys_thread_count(&optee->call_queue))) {
+		sess->use_sys_thread = true;
+		rc = 0;
+	}
+
+	mutex_unlock(&ctxdata->mutex);
+
+	return rc;
+}
+
 int optee_close_session_helper(struct tee_context *ctx, u32 session,
 			       bool system_thread)
 {
@@ -380,6 +483,9 @@ int optee_close_session_helper(struct tee_context *ctx, u32 session,
 
 	optee_free_msg_arg(ctx, entry, offs);
 
+	if (system_thread)
+		optee_cq_decr_sys_thread_count(&optee->call_queue);
+
 	return 0;
 }
 

drivers/tee/optee/ffa_abi.c

@@ -853,8 +853,7 @@ static int optee_ffa_probe(struct ffa_device *ffa_dev)
 	if (rc)
 		goto err_unreg_supp_teedev;
 	mutex_init(&optee->ffa.mutex);
-	mutex_init(&optee->call_queue.mutex);
+	optee_cq_init(&optee->call_queue, 0);
-	INIT_LIST_HEAD(&optee->call_queue.waiters);
 	optee_supp_init(&optee->supp);
 	optee_shm_arg_cache_init(optee, arg_cache_flags);
 	ffa_dev_set_drvdata(ffa_dev, optee);

drivers/tee/optee/optee_private.h

@@ -40,15 +40,33 @@ typedef void (optee_invoke_fn)(unsigned long, unsigned long, unsigned long,
 				unsigned long, unsigned long,
 				struct arm_smccc_res *);
 
+/*
+ * struct optee_call_waiter - TEE entry may need to wait for a free TEE thread
+ * @list_node		Reference in waiters list
+ * @c			Waiting completion reference
+ * @sys_thread		True if waiter belongs to a system thread
+ */
 struct optee_call_waiter {
 	struct list_head list_node;
 	struct completion c;
+	bool sys_thread;
 };
 
+/*
+ * struct optee_call_queue - OP-TEE call queue management
+ * @mutex			Serializes access to this struct
+ * @waiters			List of threads waiting to enter OP-TEE
+ * @total_thread_count		Overall number of thread context in OP-TEE or 0
+ * @free_thread_count		Number of threads context free in OP-TEE
+ * @sys_thread_req_count	Number of registered system thread sessions
+ */
 struct optee_call_queue {
 	/* Serializes access to this struct */
 	struct mutex mutex;
 	struct list_head waiters;
+	int total_thread_count;
+	int free_thread_count;
+	int sys_thread_req_count;
 };
 
 struct optee_notif {
@@ -252,6 +270,7 @@ int optee_supp_send(struct tee_context *ctx, u32 ret, u32 num_params,
 int optee_open_session(struct tee_context *ctx,
 		       struct tee_ioctl_open_session_arg *arg,
 		       struct tee_param *param);
+int optee_system_session(struct tee_context *ctx, u32 session);
 int optee_close_session_helper(struct tee_context *ctx, u32 session,
 			       bool system_thread);
 int optee_close_session(struct tee_context *ctx, u32 session);
@@ -301,6 +320,7 @@ static inline void optee_to_msg_param_value(struct optee_msg_param *mp,
 	mp->u.value.c = p->u.value.c;
 }
 
+void optee_cq_init(struct optee_call_queue *cq, int thread_count);
 void optee_cq_wait_init(struct optee_call_queue *cq,
 			struct optee_call_waiter *w, bool sys_thread);
 void optee_cq_wait_for_completion(struct optee_call_queue *cq,

drivers/tee/optee/smc_abi.c

@@ -1212,6 +1212,7 @@ static const struct tee_driver_ops optee_clnt_ops = {
 	.release = optee_release,
 	.open_session = optee_open_session,
 	.close_session = optee_close_session,
+	.system_session = optee_system_session,
 	.invoke_func = optee_invoke_func,
 	.cancel_req = optee_cancel_req,
 	.shm_register = optee_shm_register,
@@ -1359,6 +1360,16 @@ static bool optee_msg_exchange_capabilities(optee_invoke_fn *invoke_fn,
 	return true;
 }
 
+static unsigned int optee_msg_get_thread_count(optee_invoke_fn *invoke_fn)
+{
+	struct arm_smccc_res res;
+
+	invoke_fn(OPTEE_SMC_GET_THREAD_COUNT, 0, 0, 0, 0, 0, 0, 0, &res);
+	if (res.a0)
+		return 0;
+	return res.a1;
+}
+
 static struct tee_shm_pool *
 optee_config_shm_memremap(optee_invoke_fn *invoke_fn, void **memremaped_shm)
 {
@@ -1611,6 +1622,7 @@ static int optee_probe(struct platform_device *pdev)
 	struct optee *optee = NULL;
 	void *memremaped_shm = NULL;
 	unsigned int rpc_param_count;
+	unsigned int thread_count;
 	struct tee_device *teedev;
 	struct tee_context *ctx;
 	u32 max_notif_value;
@@ -1638,6 +1650,7 @@ static int optee_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
+	thread_count = optee_msg_get_thread_count(invoke_fn);
 	if (!optee_msg_exchange_capabilities(invoke_fn, &sec_caps,
 					     &max_notif_value,
 					     &rpc_param_count)) {
@@ -1727,8 +1740,7 @@ static int optee_probe(struct platform_device *pdev)
 	if (rc)
 		goto err_unreg_supp_teedev;
 
-	mutex_init(&optee->call_queue.mutex);
+	optee_cq_init(&optee->call_queue, thread_count);
-	INIT_LIST_HEAD(&optee->call_queue.waiters);
 	optee_supp_init(&optee->supp);
 	optee->smc.memremaped_shm = memremaped_shm;
 	optee->pool = pool;