s390/zcrypt/pkey: introduce zcrypt_wait_api_operational() function

The zcrypt api provides a new function to wait until the zcrypt
api is operational:

  int zcrypt_wait_api_operational(void);

The AP bus scan and the binding of ap devices to device drivers is
an asynchronous job. This function waits until these initial jobs
are done and so the zcrypt api should be ready to serve crypto
requests - if there are resources available. The function uses an
internal timeout of 60s. The very first caller will either wait for
ap bus bindings complete or the timeout happens. This state will be
remembered for further callers which will only be blocked until a
decision is made (timeout or bindings complete).

Reviewed-by: Ingo Franzki <ifranzki@linux.ibm.com>
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

1 files changed, 66 insertions, 0 deletions

diff --git a/drivers/s390/crypto/zcrypt_api.c b/drivers/s390/crypto/zcrypt_api.c
index f60f9fb25214..10206e4498d0 100644
--- a/drivers/s390/crypto/zcrypt_api.c
+++ b/drivers/s390/crypto/zcrypt_api.c
@@ -1992,6 +1992,72 @@ void zcrypt_rng_device_remove(void)
 	mutex_unlock(&zcrypt_rng_mutex);
 }
 
+/*
+ * Wait until the zcrypt api is operational.
+ * The AP bus scan and the binding of ap devices to device drivers is
+ * an asynchronous job. This function waits until these initial jobs
+ * are done and so the zcrypt api should be ready to serve crypto
+ * requests - if there are resources available. The function uses an
+ * internal timeout of 60s. The very first caller will either wait for
+ * ap bus bindings complete or the timeout happens. This state will be
+ * remembered for further callers which will only be blocked until a
+ * decision is made (timeout or bindings complete).
+ * On timeout -ETIME is returned, on success the return value is 0.
+ */
+int zcrypt_wait_api_operational(void)
+{
+	static DEFINE_MUTEX(zcrypt_wait_api_lock);
+	static int zcrypt_wait_api_state;
+	int rc;
+
+	rc = mutex_lock_interruptible(&zcrypt_wait_api_lock);
+	if (rc)
+		return rc;
+
+	switch (zcrypt_wait_api_state) {
+	case 0:
+		/* initial state, invoke wait for the ap bus complete */
+		rc = ap_wait_init_apqn_bindings_complete(
+			msecs_to_jiffies(60 * 1000));
+		switch (rc) {
+		case 0:
+			/* ap bus bindings are complete */
+			zcrypt_wait_api_state = 1;
+			break;
+		case -EINTR:
+			/* interrupted, go back to caller */
+			break;
+		case -ETIME:
+			/* timeout */
+			ZCRYPT_DBF(DBF_WARN,
+				   "%s ap_wait_init_apqn_bindings_complete() returned with ETIME\n",
+				   __func__);
+			zcrypt_wait_api_state = -ETIME;
+			break;
+		default:
+			/* other failure */
+			ZCRYPT_DBF(DBF_DEBUG,
+				   "%s ap_wait_init_apqn_bindings_complete() failure rc=%d\n",
+				   __func__, rc);
+			break;
+		}
+		break;
+	case 1:
+		/* a previous caller already found ap bus bindings complete */
+		rc = 0;
+		break;
+	default:
+		/* a previous caller had timeout or other failure */
+		rc = zcrypt_wait_api_state;
+		break;
+	}
+
+	mutex_unlock(&zcrypt_wait_api_lock);
+
+	return rc;
+}
+EXPORT_SYMBOL(zcrypt_wait_api_operational);
+
 int __init zcrypt_debug_init(void)
 {
 	zcrypt_dbf_info = debug_register("zcrypt", 1, 1,