crypto: nx - fix limits to sg lists for AES-CBC

This patch updates the nx-aes-cbc implementation to perform several
hyper calls if needed in order to always respect the length limits for
scatter/gather lists.

Two different limits are considered:

 - "ibm,max-sg-len": maximum number of bytes of each scatter/gather
   list.

 - "ibm,max-sync-cop":
    - The total number of bytes that a scatter/gather list can hold.
    - The maximum number of elements that a scatter/gather list can have.
Reviewed-by: Joy Latten <jmlatten@linux.vnet.ibm.com>
Signed-off-by: Marcelo Cerri <mhcerri@linux.vnet.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/nx/nx-aes-cbc.c

@@ -71,22 +71,29 @@ static int cbc_aes_nx_crypt(struct blkcipher_desc *desc,
 	struct nx_crypto_ctx *nx_ctx = crypto_blkcipher_ctx(desc->tfm);
 	struct nx_csbcpb *csbcpb = nx_ctx->csbcpb;
 	unsigned long irq_flags;
+	unsigned int processed = 0, to_process;
+	u32 max_sg_len;
 	int rc;
 
 	spin_lock_irqsave(&nx_ctx->lock, irq_flags);
 
-	if (nbytes > nx_ctx->ap->databytelen) {
-		rc = -EINVAL;
-		goto out;
-	}
+	max_sg_len = min_t(u32, nx_driver.of.max_sg_len/sizeof(struct nx_sg),
+			   nx_ctx->ap->sglen);
 
 	if (enc)
 		NX_CPB_FDM(csbcpb) |= NX_FDM_ENDE_ENCRYPT;
 	else
 		NX_CPB_FDM(csbcpb) &= ~NX_FDM_ENDE_ENCRYPT;
 
-	rc = nx_build_sg_lists(nx_ctx, desc, dst, src, nbytes, 0,
-			       csbcpb->cpb.aes_cbc.iv);
+	do {
+		to_process = min_t(u64, nbytes - processed,
+				   nx_ctx->ap->databytelen);
+		to_process = min_t(u64, to_process,
+				   NX_PAGE_SIZE * (max_sg_len - 1));
+		to_process = to_process & ~(AES_BLOCK_SIZE - 1);
+
+		rc = nx_build_sg_lists(nx_ctx, desc, dst, src, to_process,
+				       processed, csbcpb->cpb.aes_cbc.iv);
 		if (rc)
 			goto out;
 
@@ -104,6 +111,9 @@ static int cbc_aes_nx_crypt(struct blkcipher_desc *desc,
 		atomic_inc(&(nx_ctx->stats->aes_ops));
 		atomic64_add(csbcpb->csb.processed_byte_count,
 			     &(nx_ctx->stats->aes_bytes));
+
+		processed += to_process;
+	} while (processed < nbytes);
 out:
 	spin_unlock_irqrestore(&nx_ctx->lock, irq_flags);
 	return rc;