optee: add asynchronous notifications

Adds support for asynchronous notifications from secure world to normal
world. This allows a design with a top half and bottom half type of
driver where the top half runs in secure interrupt context and a
notifications tells normal world to schedule a yielding call to do the
bottom half processing.

The protocol is defined in optee_msg.h optee_rpc_cmd.h and optee_smc.h.

A notification consists of a 32-bit value which normal world can
retrieve using a fastcall into secure world. The value
OPTEE_SMC_ASYNC_NOTIF_VALUE_DO_BOTTOM_HALF (0) has a special meaning.
When this value is sent it means that normal world is supposed to make a
yielding call OPTEE_MSG_CMD_DO_BOTTOM_HALF.

Notification capability is negotiated while the driver is initialized.
If both sides supports these notifications then they are enabled.

An interrupt is used to notify the driver that there are asynchronous
notifications pending. The maximum needed notification value is
communicated at this stage. This allows scaling up when needed.
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

drivers/tee/optee/optee_msg.h

@@ -318,6 +318,13 @@ struct optee_msg_arg {
  * [in] param[0].u.rmem.shm_ref		holds shared memory reference
  * [in] param[0].u.rmem.offs		0
  * [in] param[0].u.rmem.size		0
+ *
+ * OPTEE_MSG_CMD_DO_BOTTOM_HALF does the scheduled bottom half processing
+ * of a driver.
+ *
+ * OPTEE_MSG_CMD_STOP_ASYNC_NOTIF informs secure world that from now is
+ * normal world unable to process asynchronous notifications. Typically
+ * used when the driver is shut down.
  */
 #define OPTEE_MSG_CMD_OPEN_SESSION	0
 #define OPTEE_MSG_CMD_INVOKE_COMMAND	1
@@ -325,6 +332,8 @@ struct optee_msg_arg {
 #define OPTEE_MSG_CMD_CANCEL		3
 #define OPTEE_MSG_CMD_REGISTER_SHM	4
 #define OPTEE_MSG_CMD_UNREGISTER_SHM	5
+#define OPTEE_MSG_CMD_DO_BOTTOM_HALF	6
+#define OPTEE_MSG_CMD_STOP_ASYNC_NOTIF	7
 #define OPTEE_MSG_FUNCID_CALL_WITH_ARG	0x0004
 
 #endif /* _OPTEE_MSG_H */

drivers/tee/optee/optee_private.h

@@ -53,6 +53,7 @@ struct optee_call_queue {
 
 struct optee_notif {
 	u_int max_key;
+	struct tee_context *ctx;
 	/* Serializes access to the elements below in this struct */
 	spinlock_t lock;
 	struct list_head db;
@@ -88,6 +89,7 @@ struct optee_smc {
 	optee_invoke_fn *invoke_fn;
 	void *memremaped_shm;
 	u32 sec_caps;
+	unsigned int notif_irq;
 };
 
 /**

drivers/tee/optee/optee_smc.h

@@ -107,6 +107,12 @@ struct optee_smc_call_get_os_revision_result {
 /*
  * Call with struct optee_msg_arg as argument
  *
+ * When calling this function normal world has a few responsibilities:
+ * 1. It must be able to handle eventual RPCs
+ * 2. Non-secure interrupts should not be masked
+ * 3. If asynchronous notifications has been negotiated successfully, then
+ *    asynchronous notifications should be unmasked during this call.
+ *
  * Call register usage:
  * a0	SMC Function ID, OPTEE_SMC*CALL_WITH_ARG
  * a1	Upper 32 bits of a 64-bit physical pointer to a struct optee_msg_arg
@@ -195,7 +201,8 @@ struct optee_smc_get_shm_config_result {
  * Normal return register usage:
  * a0	OPTEE_SMC_RETURN_OK
  * a1	bitfield of secure world capabilities OPTEE_SMC_SEC_CAP_*
- * a2-7	Preserved
+ * a2	The maximum secure world notification number
+ * a3-7	Preserved
  *
  * Error return register usage:
  * a0	OPTEE_SMC_RETURN_ENOTAVAIL, can't use the capabilities from normal world
@@ -218,6 +225,8 @@ struct optee_smc_get_shm_config_result {
 #define OPTEE_SMC_SEC_CAP_VIRTUALIZATION	BIT(3)
 /* Secure world supports Shared Memory with a NULL reference */
 #define OPTEE_SMC_SEC_CAP_MEMREF_NULL		BIT(4)
+/* Secure world supports asynchronous notification of normal world */
+#define OPTEE_SMC_SEC_CAP_ASYNC_NOTIF		BIT(5)
 
 #define OPTEE_SMC_FUNCID_EXCHANGE_CAPABILITIES	9
 #define OPTEE_SMC_EXCHANGE_CAPABILITIES \
@@ -226,8 +235,8 @@ struct optee_smc_get_shm_config_result {
 struct optee_smc_exchange_capabilities_result {
 	unsigned long status;
 	unsigned long capabilities;
+	unsigned long max_notif_value;
 	unsigned long reserved0;
-	unsigned long reserved1;
 };
 
 /*
@@ -319,6 +328,68 @@ struct optee_smc_disable_shm_cache_result {
 #define OPTEE_SMC_GET_THREAD_COUNT \
 	OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_GET_THREAD_COUNT)
 
+/*
+ * Inform OP-TEE that normal world is able to receive asynchronous
+ * notifications.
+ *
+ * Call requests usage:
+ * a0	SMC Function ID, OPTEE_SMC_ENABLE_ASYNC_NOTIF
+ * a1-6	Not used
+ * a7	Hypervisor Client ID register
+ *
+ * Normal return register usage:
+ * a0	OPTEE_SMC_RETURN_OK
+ * a1-7	Preserved
+ *
+ * Not supported return register usage:
+ * a0	OPTEE_SMC_RETURN_ENOTAVAIL
+ * a1-7	Preserved
+ */
+#define OPTEE_SMC_FUNCID_ENABLE_ASYNC_NOTIF	16
+#define OPTEE_SMC_ENABLE_ASYNC_NOTIF \
+	OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_ENABLE_ASYNC_NOTIF)
+
+/*
+ * Retrieve a value of notifications pending since the last call of this
+ * function.
+ *
+ * OP-TEE keeps a record of all posted values. When an interrupt is
+ * received which indicates that there are posted values this function
+ * should be called until all pended values have been retrieved. When a
+ * value is retrieved, it's cleared from the record in secure world.
+ *
+ * Call requests usage:
+ * a0	SMC Function ID, OPTEE_SMC_GET_ASYNC_NOTIF_VALUE
+ * a1-6	Not used
+ * a7	Hypervisor Client ID register
+ *
+ * Normal return register usage:
+ * a0	OPTEE_SMC_RETURN_OK
+ * a1	value
+ * a2	Bit[0]: OPTEE_SMC_ASYNC_NOTIF_VALUE_VALID if the value in a1 is
+ *		valid, else 0 if no values where pending
+ * a2	Bit[1]: OPTEE_SMC_ASYNC_NOTIF_VALUE_PENDING if another value is
+ *		pending, else 0.
+ *	Bit[31:2]: MBZ
+ * a3-7	Preserved
+ *
+ * Not supported return register usage:
+ * a0	OPTEE_SMC_RETURN_ENOTAVAIL
+ * a1-7	Preserved
+ */
+#define OPTEE_SMC_ASYNC_NOTIF_VALUE_VALID	BIT(0)
+#define OPTEE_SMC_ASYNC_NOTIF_VALUE_PENDING	BIT(1)
+
+/*
+ * Notification that OP-TEE expects a yielding call to do some bottom half
+ * work in a driver.
+ */
+#define OPTEE_SMC_ASYNC_NOTIF_VALUE_DO_BOTTOM_HALF	0
+
+#define OPTEE_SMC_FUNCID_GET_ASYNC_NOTIF_VALUE	17
+#define OPTEE_SMC_GET_ASYNC_NOTIF_VALUE \
+	OPTEE_SMC_FAST_CALL_VAL(OPTEE_SMC_FUNCID_GET_ASYNC_NOTIF_VALUE)
+
 /*
  * Resume from RPC (for example after processing a foreign interrupt)
  *

drivers/tee/optee/smc_abi.c

@@ -8,13 +8,16 @@
 
 #include <linux/arm-smccc.h>
 #include <linux/errno.h>
+#include <linux/interrupt.h>
 #include <linux/io.h>
-#include <linux/sched.h>
+#include <linux/irqdomain.h>
 #include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_irq.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
+#include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/tee_drv.h>
@@ -34,7 +37,8 @@
  * 2. Low level support functions to register shared memory in secure world
  * 3. Dynamic shared memory pool based on alloc_pages()
  * 4. Do a normal scheduled call into secure world
- * 5. Driver initialization.
+ * 5. Asynchronous notification
+ * 6. Driver initialization.
  */
 
 #define OPTEE_SHM_NUM_PRIV_PAGES	CONFIG_OPTEE_SHM_NUM_PRIV_PAGES
@@ -875,10 +879,137 @@ static int optee_smc_do_call_with_arg(struct tee_context *ctx,
 	return rc;
 }
 
+static int simple_call_with_arg(struct tee_context *ctx, u32 cmd)
+{
+	struct optee_msg_arg *msg_arg;
+	struct tee_shm *shm;
+
+	shm = optee_get_msg_arg(ctx, 0, &msg_arg);
+	if (IS_ERR(shm))
+		return PTR_ERR(shm);
+
+	msg_arg->cmd = cmd;
+	optee_smc_do_call_with_arg(ctx, shm);
+
+	tee_shm_free(shm);
+	return 0;
+}
+
+static int optee_smc_do_bottom_half(struct tee_context *ctx)
+{
+	return simple_call_with_arg(ctx, OPTEE_MSG_CMD_DO_BOTTOM_HALF);
+}
+
+static int optee_smc_stop_async_notif(struct tee_context *ctx)
+{
+	return simple_call_with_arg(ctx, OPTEE_MSG_CMD_STOP_ASYNC_NOTIF);
+}
+
 /*
- * 5. Driver initialization
+ * 5. Asynchronous notification
+ */
+
+static u32 get_async_notif_value(optee_invoke_fn *invoke_fn, bool *value_valid,
+				 bool *value_pending)
+{
+	struct arm_smccc_res res;
+
+	invoke_fn(OPTEE_SMC_GET_ASYNC_NOTIF_VALUE, 0, 0, 0, 0, 0, 0, 0, &res);
+
+	if (res.a0)
+		return 0;
+	*value_valid = (res.a2 & OPTEE_SMC_ASYNC_NOTIF_VALUE_VALID);
+	*value_pending = (res.a2 & OPTEE_SMC_ASYNC_NOTIF_VALUE_PENDING);
+	return res.a1;
+}
+
+static irqreturn_t notif_irq_handler(int irq, void *dev_id)
+{
+	struct optee *optee = dev_id;
+	bool do_bottom_half = false;
+	bool value_valid;
+	bool value_pending;
+	u32 value;
+
+	do {
+		value = get_async_notif_value(optee->smc.invoke_fn,
+					      &value_valid, &value_pending);
+		if (!value_valid)
+			break;
+
+		if (value == OPTEE_SMC_ASYNC_NOTIF_VALUE_DO_BOTTOM_HALF)
+			do_bottom_half = true;
+		else
+			optee_notif_send(optee, value);
+	} while (value_pending);
+
+	if (do_bottom_half)
+		return IRQ_WAKE_THREAD;
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t notif_irq_thread_fn(int irq, void *dev_id)
+{
+	struct optee *optee = dev_id;
+
+	optee_smc_do_bottom_half(optee->notif.ctx);
+
+	return IRQ_HANDLED;
+}
+
+static int optee_smc_notif_init_irq(struct optee *optee, u_int irq)
+{
+	struct tee_context *ctx;
+	int rc;
+
+	ctx = teedev_open(optee->teedev);
+	if (IS_ERR(ctx))
+		return PTR_ERR(ctx);
+
+	optee->notif.ctx = ctx;
+	rc = request_threaded_irq(irq, notif_irq_handler,
+				  notif_irq_thread_fn,
+				  0, "optee_notification", optee);
+	if (rc)
+		goto err_close_ctx;
+
+	optee->smc.notif_irq = irq;
+
+	return 0;
+
+err_close_ctx:
+	teedev_close_context(optee->notif.ctx);
+	optee->notif.ctx = NULL;
+
+	return rc;
+}
+
+static void optee_smc_notif_uninit_irq(struct optee *optee)
+{
+	if (optee->notif.ctx) {
+		optee_smc_stop_async_notif(optee->notif.ctx);
+		if (optee->smc.notif_irq) {
+			free_irq(optee->smc.notif_irq, optee);
+			irq_dispose_mapping(optee->smc.notif_irq);
+		}
+
+		/*
+		 * The thread normally working with optee->notif.ctx was
+		 * stopped with free_irq() above.
 		 *
- * During driver inititialization is secure world probed to find out which
+		 * Note we're not using teedev_close_context() or
+		 * tee_client_close_context() since we have already called
+		 * tee_device_put() while initializing to avoid a circular
+		 * reference counting.
+		 */
+		teedev_close_context(optee->notif.ctx);
+	}
+}
+
+/*
+ * 6. Driver initialization
+ *
+ * During driver initialization is secure world probed to find out which
  * features it supports so the driver can be initialized with a matching
  * configuration. This involves for instance support for dynamic shared
  * memory instead of a static memory carvout.
@@ -950,6 +1081,17 @@ static const struct optee_ops optee_ops = {
 	.from_msg_param = optee_from_msg_param,
 };
 
+static int enable_async_notif(optee_invoke_fn *invoke_fn)
+{
+	struct arm_smccc_res res;
+
+	invoke_fn(OPTEE_SMC_ENABLE_ASYNC_NOTIF, 0, 0, 0, 0, 0, 0, 0, &res);
+
+	if (res.a0)
+		return -EINVAL;
+	return 0;
+}
+
 static bool optee_msg_api_uid_is_optee_api(optee_invoke_fn *invoke_fn)
 {
 	struct arm_smccc_res res;
@@ -999,7 +1141,7 @@ static bool optee_msg_api_revision_is_compatible(optee_invoke_fn *invoke_fn)
 }
 
 static bool optee_msg_exchange_capabilities(optee_invoke_fn *invoke_fn,
-					    u32 *sec_caps)
+					    u32 *sec_caps, u32 *max_notif_value)
 {
 	union {
 		struct arm_smccc_res smccc;
@@ -1022,6 +1164,11 @@ static bool optee_msg_exchange_capabilities(optee_invoke_fn *invoke_fn,
 		return false;
 
 	*sec_caps = res.result.capabilities;
+	if (*sec_caps & OPTEE_SMC_SEC_CAP_ASYNC_NOTIF)
+		*max_notif_value = res.result.max_notif_value;
+	else
+		*max_notif_value = OPTEE_DEFAULT_MAX_NOTIF_VALUE;
+
 	return true;
 }
 
@@ -1186,6 +1333,8 @@ static int optee_smc_remove(struct platform_device *pdev)
 	 */
 	optee_disable_shm_cache(optee);
 
+	optee_smc_notif_uninit_irq(optee);
+
 	optee_remove_common(optee);
 
 	if (optee->smc.memremaped_shm)
@@ -1215,6 +1364,7 @@ static int optee_probe(struct platform_device *pdev)
 	struct optee *optee = NULL;
 	void *memremaped_shm = NULL;
 	struct tee_device *teedev;
+	u32 max_notif_value;
 	u32 sec_caps;
 	int rc;
 
@@ -1234,7 +1384,8 @@ static int optee_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
-	if (!optee_msg_exchange_capabilities(invoke_fn, &sec_caps)) {
+	if (!optee_msg_exchange_capabilities(invoke_fn, &sec_caps,
+					     &max_notif_value)) {
 		pr_warn("capabilities mismatch\n");
 		return -EINVAL;
 	}
@@ -1257,7 +1408,7 @@ static int optee_probe(struct platform_device *pdev)
 	optee = kzalloc(sizeof(*optee), GFP_KERNEL);
 	if (!optee) {
 		rc = -ENOMEM;
-		goto err;
+		goto err_free_pool;
 	}
 
 	optee->ops = &optee_ops;
@@ -1267,24 +1418,24 @@ static int optee_probe(struct platform_device *pdev)
 	teedev = tee_device_alloc(&optee_clnt_desc, NULL, pool, optee);
 	if (IS_ERR(teedev)) {
 		rc = PTR_ERR(teedev);
-		goto err;
+		goto err_free_optee;
 	}
 	optee->teedev = teedev;
 
 	teedev = tee_device_alloc(&optee_supp_desc, NULL, pool, optee);
 	if (IS_ERR(teedev)) {
 		rc = PTR_ERR(teedev);
-		goto err;
+		goto err_unreg_teedev;
 	}
 	optee->supp_teedev = teedev;
 
 	rc = tee_device_register(optee->teedev);
 	if (rc)
-		goto err;
+		goto err_unreg_supp_teedev;
 
 	rc = tee_device_register(optee->supp_teedev);
 	if (rc)
-		goto err;
+		goto err_unreg_supp_teedev;
 
 	mutex_init(&optee->call_queue.mutex);
 	INIT_LIST_HEAD(&optee->call_queue.waiters);
@@ -1293,10 +1444,27 @@ static int optee_probe(struct platform_device *pdev)
 	optee->pool = pool;
 
 	platform_set_drvdata(pdev, optee);
-	rc = optee_notif_init(optee, OPTEE_DEFAULT_MAX_NOTIF_VALUE);
+	rc = optee_notif_init(optee, max_notif_value);
+	if (rc)
+		goto err_supp_uninit;
+
+	if (sec_caps & OPTEE_SMC_SEC_CAP_ASYNC_NOTIF) {
+		unsigned int irq;
+
+		rc = platform_get_irq(pdev, 0);
+		if (rc < 0) {
+			pr_err("platform_get_irq: ret %d\n", rc);
+			goto err_notif_uninit;
+		}
+		irq = rc;
+
+		rc = optee_smc_notif_init_irq(optee, irq);
 		if (rc) {
-		optee_remove(pdev);
-		return rc;
+			irq_dispose_mapping(irq);
+			goto err_notif_uninit;
+		}
+		enable_async_notif(optee->smc.invoke_fn);
+		pr_info("Asynchronous notifications enabled\n");
 	}
 
 	/*
@@ -1314,28 +1482,31 @@ static int optee_probe(struct platform_device *pdev)
 		pr_info("dynamic shared memory is enabled\n");
 
 	rc = optee_enumerate_devices(PTA_CMD_GET_DEVICES);
-	if (rc) {
-		optee_smc_remove(pdev);
-		return rc;
-	}
+	if (rc)
+		goto err_disable_shm_cache;
 
 	pr_info("initialized driver\n");
 	return 0;
-err:
-	if (optee) {
-		/*
-		 * tee_device_unregister() is safe to call even if the
-		 * devices hasn't been registered with
-		 * tee_device_register() yet.
-		 */
+
+err_disable_shm_cache:
+	optee_disable_shm_cache(optee);
+	optee_smc_notif_uninit_irq(optee);
+	optee_unregister_devices();
+err_notif_uninit:
+	optee_notif_uninit(optee);
+err_supp_uninit:
+	optee_supp_uninit(&optee->supp);
+	mutex_destroy(&optee->call_queue.mutex);
+err_unreg_supp_teedev:
 	tee_device_unregister(optee->supp_teedev);
+err_unreg_teedev:
 	tee_device_unregister(optee->teedev);
+err_free_optee:
 	kfree(optee);
-	}
-	if (pool)
+err_free_pool:
 	tee_shm_pool_free(pool);
-	if (memremaped_shm)
-		memunmap(memremaped_shm);
+	if (optee->smc.memremaped_shm)
+		memunmap(optee->smc.memremaped_shm);
 	return rc;
 }