[PATCH] s390/zcrypt: enable s390 hwrng to seed kernel entropy

[Ingo Tuchscherer <ingo.tuchscherer@de.ibm.com>]

Set the 'quality' property in the zcrypt rng device structure to enable the
zcrypt hwrng device to take part in the kernel entropy seeding process.
A module parameter named hwrng_seed will be introduced to disable the
participation. By default this parameter is set to 1 (enabled).

Signed-off-by: Ingo Tuchscherer <ingo.tuchscherer@de.ibm.com>
---
 drivers/s390/crypto/ap_bus.c     | 5 +++++
 drivers/s390/crypto/ap_bus.h     | 1 +
 drivers/s390/crypto/zcrypt_api.c | 3 +++
 3 files changed, 9 insertions(+)

diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
index 4038437..19fac5f 100644
--- a/drivers/s390/crypto/ap_bus.c
+++ b/drivers/s390/crypto/ap_bus.c
@@ -85,6 +85,11 @@ static int ap_thread_flag = 0;
 module_param_named(poll_thread, ap_thread_flag, int, S_IRUSR|S_IRGRP);
 MODULE_PARM_DESC(poll_thread, "Turn on/off poll thread, default is 0 (off).");
 
+int ap_hwrng_seed = 1;
+EXPORT_SYMBOL(ap_hwrng_seed);
+module_param_named(hwrng_seed, ap_hwrng_seed, int, S_IRUSR|S_IRGRP);
+MODULE_PARM_DESC(hwrng_seed, "Turn on/off hwrng auto seed, default is 1 (on).");
+
 static struct device *ap_root_device = NULL;
 static struct ap_config_info *ap_configuration;
 static DEFINE_SPINLOCK(ap_device_list_lock);
diff --git a/drivers/s390/crypto/ap_bus.h b/drivers/s390/crypto/ap_bus.h
index 6405ae2..b0be09a 100644
--- a/drivers/s390/crypto/ap_bus.h
+++ b/drivers/s390/crypto/ap_bus.h
@@ -38,6 +38,7 @@
 #define AP_POLL_TIME 1		/* Time in ticks between receive polls. */
 
 extern int ap_domain_index;
+extern int ap_hwrng_seed;
 
 /**
  * The ap_qid_t identifier of an ap queue. It contains a
diff --git a/drivers/s390/crypto/zcrypt_api.c b/drivers/s390/crypto/zcrypt_api.c
index 0e18c5d..ed91665 100644
--- a/drivers/s390/crypto/zcrypt_api.c
+++ b/drivers/s390/crypto/zcrypt_api.c
@@ -1374,6 +1374,7 @@ static int zcrypt_rng_data_read(struct hwrng *rng, u32 *data)
 static struct hwrng zcrypt_rng_dev = {
 	.name		= "zcrypt",
 	.data_read	= zcrypt_rng_data_read,
+	.quality	= 990,
 };
 
 static int zcrypt_rng_device_add(void)
@@ -1388,6 +1389,8 @@ static int zcrypt_rng_device_add(void)
 			goto out;
 		}
 		zcrypt_rng_buffer_index = 0;
+		if (!ap_hwrng_seed)
+			zcrypt_rng_dev.quality = 0;
 		rc = hwrng_register(&zcrypt_rng_dev);
 		if (rc)
 			goto out_free;
-- 
1.8.5.5