s390/pkey/crypto: Introduce xflags param for pkey in-kernel API

Add a new parameter xflags to the in-kernel API function
pkey_key2protkey(). Currently there is only one flag supported:

* PKEY_XFLAG_NOMEMALLOC:
If this flag is given in the xflags parameter, the pkey
implementation is not allowed to allocate memory but instead should
fall back to use preallocated memory or simple fail with -ENOMEM.
This flag is for protected key derive within a cipher or similar
which must not allocate memory which would cause io operations - see
also the CRYPTO_ALG_ALLOCATES_MEMORY flag in crypto.h.

The one and only user of this in-kernel API - the skcipher
implementations PAES in paes_s390.c set this flag upon request
to derive a protected key from the given raw key material.

Signed-off-by: Harald Freudenberger <[e-mail]>
Reviewed-by: Holger Dengler <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Heiko Carstens <[e-mail]>

arch/s390/crypto/paes_s390.c

···
 {
 	int i, rc = -EIO;
 
-	/* try three times in case of busy card */
+	/* try three times in case of busy card or no mem */
 	for (i = 0; rc && i < 3; i++) {
-		if (rc == -EBUSY && in_task()) {
+		if ((rc == -EBUSY || rc == -ENOMEM) && in_task()) {
 			if (msleep_interruptible(1000))
 				return -EINTR;
 		}
 		rc = pkey_key2protkey(key, keylen, pk->protkey, &pk->len,
-				      &pk->type);
+				      &pk->type, PKEY_XFLAG_NOMEMALLOC);
 	}
 
 	return rc;

arch/s390/include/asm/pkey.h

···
  * @param key pointer to a buffer containing the key blob
  * @param keylen size of the key blob in bytes
  * @param protkey pointer to buffer receiving the protected key
+ * @param xflags additional execution flags (see PKEY_XFLAG_* definitions below)
+ *	  As of now the only supported flag is PKEY_XFLAG_NOMEMALLOC.
  * @return 0 on success, negative errno value on failure
  */
 int pkey_key2protkey(const u8 *key, u32 keylen,
-		     u8 *protkey, u32 *protkeylen, u32 *protkeytype);
+		     u8 *protkey, u32 *protkeylen, u32 *protkeytype,
+		     u32 xflags);
 
 /*
  * If this flag is given in the xflags parameter, the pkey implementation

drivers/s390/crypto/pkey_api.c

···
  * In-Kernel function: Transform a key blob (of any type) into a protected key
  */
 int pkey_key2protkey(const u8 *key, u32 keylen,
-		     u8 *protkey, u32 *protkeylen, u32 *protkeytype)
+		     u8 *protkey, u32 *protkeylen, u32 *protkeytype, u32 xflags)
 {
 	int rc;
-	const u32 xflags = 0;
 
 	rc = key2protkey(NULL, 0, key, keylen,
 			 protkey, protkeylen, protkeytype, xflags);