s390/zcrypt: Introduce pre-allocated device status array for cca misc

Introduce a pre-allocated device status array memory together with
a mutex controlling the occupation to be used by the findcard2()
function. Limit the device status array to max 128 cards and max
128 domains to reduce the size of this pre-allocated memory to 64 KB.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Link: https://lore.kernel.org/r/20250424133619.16495-10-freude@linux.ibm.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Author: hfreude

drivers/s390/crypto/zcrypt_ccamisc.c

@@ -51,6 +51,22 @@ static DEFINE_SPINLOCK(cca_info_list_lock);
 #define CPRB_MEMPOOL_ITEM_SIZE (16 * 1024)
 static mempool_t *cprb_mempool;
 
+/*
+ * This is a pre-allocated memory for the device status array
+ * used within the findcard() functions. It is currently
+ * 128 * 128 * 4 bytes = 64 KB big. Usage of this memory is
+ * controlled via dev_status_mem_mutex. Needs adaption if more
+ * than 128 cards or domains to be are supported.
+ */
+#define ZCRYPT_DEV_STATUS_CARD_MAX 128
+#define ZCRYPT_DEV_STATUS_QUEUE_MAX 128
+#define ZCRYPT_DEV_STATUS_ENTRIES (ZCRYPT_DEV_STATUS_CARD_MAX * \
+				   ZCRYPT_DEV_STATUS_QUEUE_MAX)
+#define ZCRYPT_DEV_STATUS_EXT_SIZE (ZCRYPT_DEV_STATUS_ENTRIES * \
+		sizeof(struct zcrypt_device_status_ext))
+static void *dev_status_mem;
+static DEFINE_MUTEX(dev_status_mem_mutex);
+
 /*
  * Simple check if the token is a valid CCA secure AES data key
  * token. If keybitsize is given, the bitsize of the key is
@@ -1919,16 +1935,15 @@ int cca_findcard2(u32 **apqns, u32 *nr_apqns, u16 cardnr, u16 domain,
 	int i, card, dom, curmatch, oldmatch, rc;
 	struct cca_info ci;
 
-	/* fetch status of all crypto cards */
-	device_status = kvcalloc(MAX_ZDEV_ENTRIES_EXT,
-				 sizeof(struct zcrypt_device_status_ext),
-				 GFP_KERNEL);
-	if (!device_status)
-		return -ENOMEM;
+	/* occupy the device status memory */
+	mutex_lock(&dev_status_mem_mutex);
+	memset(dev_status_mem, 0, ZCRYPT_DEV_STATUS_EXT_SIZE);
+	device_status = (struct zcrypt_device_status_ext *)dev_status_mem;
 
+	/* fetch crypto device status into this struct */
 	zcrypt_device_status_mask_ext(device_status,
-				      MAX_ZDEV_CARDIDS_EXT,
-				      MAX_ZDEV_DOMAINS_EXT);
+				      ZCRYPT_DEV_STATUS_CARD_MAX,
+				      ZCRYPT_DEV_STATUS_QUEUE_MAX);
 
 	/* allocate 1k space for up to 256 apqns */
 	_apqns = kmalloc_array(256, sizeof(u32), GFP_KERNEL);
@@ -1938,7 +1953,7 @@ int cca_findcard2(u32 **apqns, u32 *nr_apqns, u16 cardnr, u16 domain,
 	}
 
 	/* walk through all the crypto apqnss */
-	for (i = 0; i < MAX_ZDEV_ENTRIES_EXT; i++) {
+	for (i = 0; i < ZCRYPT_DEV_STATUS_ENTRIES; i++) {
 		card = AP_QID_CARD(device_status[i].qid);
 		dom = AP_QID_QUEUE(device_status[i].qid);
 		/* check online state */
@@ -2000,7 +2015,9 @@ int cca_findcard2(u32 **apqns, u32 *nr_apqns, u16 cardnr, u16 domain,
 	}
 
 out:
-	kvfree(device_status);
+	/* release the device status memory */
+	mutex_unlock(&dev_status_mem_mutex);
+
 	return rc;
 }
 EXPORT_SYMBOL(cca_findcard2);
@@ -2013,11 +2030,21 @@ int __init zcrypt_ccamisc_init(void)
 	if (!cprb_mempool)
 		return -ENOMEM;
 
+	/* Pre-allocate one crypto status card struct used in findcard() */
+	dev_status_mem = kvmalloc(ZCRYPT_DEV_STATUS_EXT_SIZE, GFP_KERNEL);
+	if (!dev_status_mem) {
+		mempool_destroy(cprb_mempool);
+		return -ENOMEM;
+	}
+
 	return 0;
 }
 
 void zcrypt_ccamisc_exit(void)
 {
 	mkvp_cache_free();
+	mutex_lock(&dev_status_mem_mutex);
+	kvfree(dev_status_mem);
+	mutex_unlock(&dev_status_mem_mutex);
 	mempool_destroy(cprb_mempool);
 }