linux-kernel - [PATCH v6 08/11] crypto: qce: skcipher: Improve the conditions for requesting AES fallback cipher

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Date:   Sun,  7 Feb 2021 09:39:43 -0500
From:   Thara Gopinath <thara.gopinath@...aro.org>
To:     herbert@...dor.apana.org.au, davem@...emloft.net,
        bjorn.andersson@...aro.org
Cc:     ebiggers@...gle.com, ardb@...nel.org, sivaprak@...eaurora.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v6 08/11] crypto: qce: skcipher: Improve the conditions for requesting AES fallback cipher

The following are the conditions for requesting AES fallback cipher.
	-  AES-192
	- AES-XTS request with len <= 512 byte (Allow messages of length
	  less than 512 bytes for all other AES encryption algorithms other
	  than AES XTS)
	- AES-XTS request with len > QCE_SECTOR_SIZE and is not a multiple
	  of it

Signed-off-by: Thara Gopinath <thara.gopinath@...aro.org>
---
 drivers/crypto/qce/skcipher.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/crypto/qce/skcipher.c b/drivers/crypto/qce/skcipher.c
index 64f661d7335f..66a226d1205e 100644
--- a/drivers/crypto/qce/skcipher.c
+++ b/drivers/crypto/qce/skcipher.c
@@ -274,14 +274,19 @@ static int qce_skcipher_crypt(struct skcipher_request *req, int encrypt)
 		if (!IS_ALIGNED(req->cryptlen, blocksize))
 			return -EINVAL;
 
-	/* qce is hanging when AES-XTS request len > QCE_SECTOR_SIZE and
-	 * is not a multiple of it; pass such requests to the fallback
+	/*
+	 * Conditions for requesting a fallback cipher
+	 * AES-192 (not supported by crypto engine (CE))
+	 * AES-XTS request with len <= 512 byte (not recommended to use CE)
+	 * AES-XTS request with len > QCE_SECTOR_SIZE and
+	 * is not a multiple of it.(Revisit this condition to check if it is
+	 * needed in all versions of CE)
 	 */
 	if (IS_AES(rctx->flags) &&
-	    (((keylen != AES_KEYSIZE_128 && keylen != AES_KEYSIZE_256) ||
-	      req->cryptlen <= aes_sw_max_len) ||
-	     (IS_XTS(rctx->flags) && req->cryptlen > QCE_SECTOR_SIZE &&
-	      req->cryptlen % QCE_SECTOR_SIZE))) {
+	    ((keylen != AES_KEYSIZE_128 && keylen != AES_KEYSIZE_256) ||
+	    (IS_XTS(rctx->flags) && ((req->cryptlen <= aes_sw_max_len) ||
+	    (req->cryptlen > QCE_SECTOR_SIZE &&
+	    req->cryptlen % QCE_SECTOR_SIZE))))) {
 		skcipher_request_set_tfm(&rctx->fallback_req, ctx->fallback);
 		skcipher_request_set_callback(&rctx->fallback_req,
 					      req->base.flags,
-- 
2.25.1