[PATCH] crypto: caam - update xts sector size for large input length

[Andrei Botila <andrei.botila@oss.nxp.com>]

From: Andrei Botila <andrei.botila@nxp.com>

Since in the software implementation of XTS-AES there is
no notion of sector every input length is processed the same way.
CAAM implementation has the notion of sector which causes different
results between the software implementation and the one in CAAM
for input lengths bigger than 512 bytes.
Increase sector size to maximum value on 16 bits.

Fixes: c6415a6016bf ("crypto: caam - add support for acipher xts(aes)")
Cc: <stable@vger.kernel.org> # v4.12+
Signed-off-by: Andrei Botila <andrei.botila@nxp.com>
---
This patch needs to be applied from v4.12+ because dm-crypt has added support
for 4K sector size at that version. The commit was
8f0009a225171 ("dm-crypt: optionally support larger encryption sector size").

 drivers/crypto/caam/caamalg_desc.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/crypto/caam/caamalg_desc.c b/drivers/crypto/caam/caamalg_desc.c
index aa9ccca67045..8ebbbd28b1f7 100644
--- a/drivers/crypto/caam/caamalg_desc.c
+++ b/drivers/crypto/caam/caamalg_desc.c
@@ -1518,7 +1518,13 @@ EXPORT_SYMBOL(cnstr_shdsc_skcipher_decap);
  */
 void cnstr_shdsc_xts_skcipher_encap(u32 * const desc, struct alginfo *cdata)
 {
-	__be64 sector_size = cpu_to_be64(512);
+	/*
+	 * Set sector size to a big value, practically disabling
+	 * sector size segmentation in xts implementation. We cannot
+	 * take full advantage of this HW feature with existing
+	 * crypto API / dm-crypt SW architecture.
+	 */
+	__be64 sector_size = cpu_to_be64(BIT(15));
 	u32 *key_jump_cmd;
 
 	init_sh_desc(desc, HDR_SHARE_SERIAL | HDR_SAVECTX);
@@ -1571,7 +1577,13 @@ EXPORT_SYMBOL(cnstr_shdsc_xts_skcipher_encap);
  */
 void cnstr_shdsc_xts_skcipher_decap(u32 * const desc, struct alginfo *cdata)
 {
-	__be64 sector_size = cpu_to_be64(512);
+	/*
+	 * Set sector size to a big value, practically disabling
+	 * sector size segmentation in xts implementation. We cannot
+	 * take full advantage of this HW feature with existing
+	 * crypto API / dm-crypt SW architecture.
+	 */
+	__be64 sector_size = cpu_to_be64(BIT(15));
 	u32 *key_jump_cmd;
 
 	init_sh_desc(desc, HDR_SHARE_SERIAL | HDR_SAVECTX);
-- 
2.17.1