[RFC] crypto: skcipher - introduce walksize attribute for SIMD algos

diff --git a/crypto/skcipher.c b/crypto/skcipher.c
index aca07c643d41..7570d7c958e8 100644
--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -185,12 +185,12 @@  void skcipher_walk_complete(struct skcipher_walk *walk, int err)
 		data = p->data;
 		if (!data) {
 			data = PTR_ALIGN(&p->buffer[0], walk->alignmask + 1);
-			data = skcipher_get_spot(data, walk->chunksize);
+			data = skcipher_get_spot(data, walk->stride);
 		}
 
 		scatterwalk_copychunks(data, &p->dst, p->len, 1);
 
-		if (offset_in_page(p->data) + p->len + walk->chunksize >
+		if (offset_in_page(p->data) + p->len + walk->stride >
 		    PAGE_SIZE)
 			free_page((unsigned long)p->data);
 
@@ -297,7 +297,7 @@  static int skcipher_next_copy(struct skcipher_walk *walk)
 	p->len = walk->nbytes;
 	skcipher_queue_write(walk, p);
 
-	if (offset_in_page(walk->page) + walk->nbytes + walk->chunksize >
+	if (offset_in_page(walk->page) + walk->nbytes + walk->stride >
 	    PAGE_SIZE)
 		walk->page = NULL;
 	else
@@ -342,7 +342,7 @@  static int skcipher_walk_next(struct skcipher_walk *walk)
 			 SKCIPHER_WALK_DIFF);
 
 	n = walk->total;
-	bsize = min(walk->chunksize, max(n, walk->blocksize));
+	bsize = min(walk->stride, max(n, walk->blocksize));
 	n = scatterwalk_clamp(&walk->in, n);
 	n = scatterwalk_clamp(&walk->out, n);
 
@@ -391,7 +391,7 @@  static int skcipher_copy_iv(struct skcipher_walk *walk)
 	unsigned a = crypto_tfm_ctx_alignment() - 1;
 	unsigned alignmask = walk->alignmask;
 	unsigned ivsize = walk->ivsize;
-	unsigned bs = walk->chunksize;
+	unsigned bs = walk->stride;
 	unsigned aligned_bs;
 	unsigned size;
 	u8 *iv;
@@ -461,7 +461,7 @@  static int skcipher_walk_skcipher(struct skcipher_walk *walk,
 		       SKCIPHER_WALK_SLEEP : 0;
 
 	walk->blocksize = crypto_skcipher_blocksize(tfm);
-	walk->chunksize = crypto_skcipher_chunksize(tfm);
+	walk->stride = crypto_skcipher_walksize(tfm);
 	walk->ivsize = crypto_skcipher_ivsize(tfm);
 	walk->alignmask = crypto_skcipher_alignmask(tfm);
 
@@ -523,7 +523,7 @@  static int skcipher_walk_aead_common(struct skcipher_walk *walk,
 		walk->flags &= ~SKCIPHER_WALK_SLEEP;
 
 	walk->blocksize = crypto_aead_blocksize(tfm);
-	walk->chunksize = crypto_aead_chunksize(tfm);
+	walk->stride = crypto_aead_chunksize(tfm);
 	walk->ivsize = crypto_aead_ivsize(tfm);
 	walk->alignmask = crypto_aead_alignmask(tfm);
 
@@ -819,6 +819,7 @@  static void crypto_skcipher_show(struct seq_file *m, struct crypto_alg *alg)
 	seq_printf(m, "max keysize  : %u\n", skcipher->max_keysize);
 	seq_printf(m, "ivsize       : %u\n", skcipher->ivsize);
 	seq_printf(m, "chunksize    : %u\n", skcipher->chunksize);
+	seq_printf(m, "walksize     : %u\n", skcipher->walksize);
 }
 
 #ifdef CONFIG_NET
@@ -891,11 +892,14 @@  static int skcipher_prepare_alg(struct skcipher_alg *alg)
 {
 	struct crypto_alg *base = &alg->base;
 
-	if (alg->ivsize > PAGE_SIZE / 8 || alg->chunksize > PAGE_SIZE / 8)
+	if (alg->ivsize > PAGE_SIZE / 8 || alg->chunksize > PAGE_SIZE / 8 ||
+	    alg->walksize > PAGE_SIZE / 8)
 		return -EINVAL;
 
 	if (!alg->chunksize)
 		alg->chunksize = base->cra_blocksize;
+	if (!alg->walksize)
+		alg->walksize = alg->chunksize;
 
 	base->cra_type = &crypto_skcipher_type2;
 	base->cra_flags &= ~CRYPTO_ALG_TYPE_MASK;
diff --git a/include/crypto/internal/skcipher.h b/include/crypto/internal/skcipher.h
index 8735979ed341..e42f7063f245 100644
--- a/include/crypto/internal/skcipher.h
+++ b/include/crypto/internal/skcipher.h
@@ -66,7 +66,7 @@  struct skcipher_walk {
 
 	int flags;
 	unsigned int blocksize;
-	unsigned int chunksize;
+	unsigned int stride;
 	unsigned int alignmask;
 };
 
diff --git a/include/crypto/skcipher.h b/include/crypto/skcipher.h
index cc4d98a7892e..3c17a33255b0 100644
--- a/include/crypto/skcipher.h
+++ b/include/crypto/skcipher.h
@@ -115,6 +115,9 @@  struct crypto_skcipher {
  *	    IV of exactly that size to perform the encrypt or decrypt operation.
  * @chunksize: Equal to the block size except for stream ciphers such as
  *	       CTR where it is set to the underlying block size.
+ * @walksize: Equal to the chunk size except in cases where the algorithm is
+ * 	      considerably more efficient if it can operate on multiple chunks
+ * 	      in parallel. Should be a multiple of chunksize.
  * @base: Definition of a generic crypto algorithm.
  *
  * All fields except @ivsize are mandatory and must be filled.
@@ -131,6 +134,7 @@  struct skcipher_alg {
 	unsigned int max_keysize;
 	unsigned int ivsize;
 	unsigned int chunksize;
+	unsigned int walksize;
 
 	struct crypto_alg base;
 };
@@ -289,6 +293,19 @@  static inline unsigned int crypto_skcipher_alg_chunksize(
 	return alg->chunksize;
 }
 
+static inline unsigned int crypto_skcipher_alg_walksize(
+	struct skcipher_alg *alg)
+{
+	if ((alg->base.cra_flags & CRYPTO_ALG_TYPE_MASK) ==
+	    CRYPTO_ALG_TYPE_BLKCIPHER)
+		return alg->base.cra_blocksize;
+
+	if (alg->base.cra_ablkcipher.encrypt)
+		return alg->base.cra_blocksize;
+
+	return alg->walksize;
+}
+
 /**
  * crypto_skcipher_chunksize() - obtain chunk size
  * @tfm: cipher handle
@@ -307,6 +324,23 @@  static inline unsigned int crypto_skcipher_chunksize(
 }
 
 /**
+ * crypto_skcipher_walksize() - obtain walk size
+ * @tfm: cipher handle
+ *
+ * In some cases, algorithms can only perform optimally when operating on
+ * multiple blocks in parallel. This is reflected by the walksize, which
+ * must be a multiple of the chunksize (or equal if the concern does not
+ * apply)
+ *
+ * Return: walk size in bytes
+ */
+static inline unsigned int crypto_skcipher_walksize(
+	struct crypto_skcipher *tfm)
+{
+	return crypto_skcipher_alg_walksize(crypto_skcipher_alg(tfm));
+}
+
+/**
  * crypto_skcipher_blocksize() - obtain block size of cipher
  * @tfm: cipher handle
  *