[PATCH v3 2/3] crypto: ccp - Rework the unit-size check for XTS-AES

[Gary R Hook]

The CCP supports a limited set of unit-size values. Change the check
for this parameter such that acceptable values match the enumeration.
Then clarify the conditions under which we must use the fallback
implementation.

Signed-off-by: Gary R Hook <gary.h...@amd.com>
---
 drivers/crypto/ccp/ccp-crypto-aes-xts.c |   57 +++++++++++--------------------
 1 file changed, 20 insertions(+), 37 deletions(-)

diff --git a/drivers/crypto/ccp/ccp-crypto-aes-xts.c 
b/drivers/crypto/ccp/ccp-crypto-aes-xts.c
index 2b5d3a62fad9..5c2df880ab48 100644
--- a/drivers/crypto/ccp/ccp-crypto-aes-xts.c
+++ b/drivers/crypto/ccp/ccp-crypto-aes-xts.c
@@ -39,46 +39,26 @@ struct ccp_unit_size_map {
        u32 value;
 };
 
-static struct ccp_unit_size_map unit_size_map[] = {
+static struct ccp_unit_size_map xts_unit_sizes[] = {
        {
-               .size   = 4096,
-               .value  = CCP_XTS_AES_UNIT_SIZE_4096,
-       },
-       {
-               .size   = 2048,
-               .value  = CCP_XTS_AES_UNIT_SIZE_2048,
-       },
-       {
-               .size   = 1024,
-               .value  = CCP_XTS_AES_UNIT_SIZE_1024,
+               .size   = 16,
+               .value  = CCP_XTS_AES_UNIT_SIZE_16,
        },
        {
-               .size   = 512,
+               .size   = 512,
                .value  = CCP_XTS_AES_UNIT_SIZE_512,
        },
        {
-               .size   = 256,
-               .value  = CCP_XTS_AES_UNIT_SIZE__LAST,
-       },
-       {
-               .size   = 128,
-               .value  = CCP_XTS_AES_UNIT_SIZE__LAST,
-       },
-       {
-               .size   = 64,
-               .value  = CCP_XTS_AES_UNIT_SIZE__LAST,
-       },
-       {
-               .size   = 32,
-               .value  = CCP_XTS_AES_UNIT_SIZE__LAST,
+               .size   = 1024,
+               .value  = CCP_XTS_AES_UNIT_SIZE_1024,
        },
        {
-               .size   = 16,
-               .value  = CCP_XTS_AES_UNIT_SIZE_16,
+               .size   = 2048,
+               .value  = CCP_XTS_AES_UNIT_SIZE_2048,
        },
        {
-               .size   = 1,
-               .value  = CCP_XTS_AES_UNIT_SIZE__LAST,
+               .size   = 4096,
+               .value  = CCP_XTS_AES_UNIT_SIZE_4096,
        },
 };
 
@@ -138,16 +118,19 @@ static int ccp_aes_xts_crypt(struct ablkcipher_request 
*req,
        if (!req->info)
                return -EINVAL;
 
+       /* Check conditions under which the CCP can fulfill a request. The
+        * device can handle input plaintext of a length that is a multiple
+        * of the unit_size, bug the crypto implementation only supports
+        * the unit_size being equal to the input length. This limits the
+        * number of scenarios we can handle.
+        */
        unit_size = CCP_XTS_AES_UNIT_SIZE__LAST;
-       if (req->nbytes <= unit_size_map[0].size) {
-               for (unit = 0; unit < ARRAY_SIZE(unit_size_map); unit++) {
-                       if (!(req->nbytes & (unit_size_map[unit].size - 1))) {
-                               unit_size = unit_size_map[unit].value;
-                               break;
-                       }
+       for (unit = 0; unit < ARRAY_SIZE(xts_unit_sizes); unit++) {
+               if (req->nbytes == xts_unit_sizes[unit].size) {
+                       unit_size = unit;
+                       break;
                }
        }
-
        if ((unit_size == CCP_XTS_AES_UNIT_SIZE__LAST) ||
            (ctx->u.aes.key_len != AES_KEYSIZE_128)) {
                SKCIPHER_REQUEST_ON_STACK(subreq, ctx->u.aes.tfm_skcipher);