crypto: skcipher - Change default sync geniv on SMP to eseqiv

As it stands we use chainiv for sync algorithms and eseqiv for
async algorithms.  However, when there is more than one CPU
chainiv forces all processing to be serialised which is usually
not what you want.  Also, the added overhead of eseqiv isn't that
great.

Therefore this patch changes the default sync geniv on SMP machines
to eseqiv.  For the odd situation where the overhead is unacceptable
then chainiv is still available as an option.

Note that on UP machines chainiv is still preferred over eseqiv
for sync algorithms.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/ablkcipher.c

@@ -14,6 +14,7 @@
  */
 
 #include <crypto/internal/skcipher.h>
+#include <linux/cpumask.h>
 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -25,6 +26,8 @@
 
 #include "internal.h"
 
+static const char *skcipher_default_geniv __read_mostly;
+
 static int setkey_unaligned(struct crypto_ablkcipher *tfm, const u8 *key,
 			    unsigned int keylen)
 {
@@ -180,7 +183,8 @@ EXPORT_SYMBOL_GPL(crypto_givcipher_type);
 
 const char *crypto_default_geniv(const struct crypto_alg *alg)
 {
-	return alg->cra_flags & CRYPTO_ALG_ASYNC ? "eseqiv" : "chainiv";
+	return alg->cra_flags & CRYPTO_ALG_ASYNC ?
+	       "eseqiv" : skcipher_default_geniv;
 }
 
 static int crypto_givcipher_default(struct crypto_alg *alg, u32 type, u32 mask)
@@ -361,3 +365,17 @@ struct crypto_ablkcipher *crypto_alloc_ablkcipher(const char *alg_name,
 	return ERR_PTR(err);
 }
 EXPORT_SYMBOL_GPL(crypto_alloc_ablkcipher);
+
+static int __init skcipher_module_init(void)
+{
+	skcipher_default_geniv = num_possible_cpus() > 1 ?
+				 "eseqiv" : "chainiv";
+	return 0;
+}
+
+static void skcipher_module_exit(void)
+{
+}
+
+module_init(skcipher_module_init);
+module_exit(skcipher_module_exit);