[PATCH v3 02/21] crypto/arm64: sm4-ce-ccm - Avoid pointless yield of the NEON unit

[Ard Biesheuvel <ardb+git@google.com>]

From: Ard Biesheuvel <ardb@kernel.org>

Kernel mode NEON sections are now preemptible on arm64, and so there is
no need to yield it when calling APIs that may sleep.

Also, move the calls to kernel_neon_end() to the same scope as
kernel_neon_begin(). This is needed for a subsequent change where a
stack buffer is allocated transparently and passed to
kernel_neon_begin().

Acked-by: Eric Biggers <ebiggers@kernel.org>
[ardb: Simplify convoluted logic]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/crypto/sm4-ce-ccm-glue.c | 25 +++++---------------
 1 file changed, 6 insertions(+), 19 deletions(-)

diff --git a/arch/arm64/crypto/sm4-ce-ccm-glue.c b/arch/arm64/crypto/sm4-ce-ccm-glue.c
index e9cc1c1364ec..e92cbdf1aaee 100644
--- a/arch/arm64/crypto/sm4-ce-ccm-glue.c
+++ b/arch/arm64/crypto/sm4-ce-ccm-glue.c
@@ -172,35 +172,22 @@ static int ccm_crypt(struct aead_request *req, struct skcipher_walk *walk,
 	if (req->assoclen)
 		ccm_calculate_auth_mac(req, mac);
 
-	while (walk->nbytes && walk->nbytes != walk->total) {
+	while (walk->nbytes) {
 		unsigned int tail = walk->nbytes % SM4_BLOCK_SIZE;
 
+		if (walk->nbytes == walk->total)
+			tail = 0;
+
 		sm4_ce_ccm_crypt(rkey_enc, walk->dst.virt.addr,
 				 walk->src.virt.addr, walk->iv,
 				 walk->nbytes - tail, mac);
 
-		kernel_neon_end();
-
 		err = skcipher_walk_done(walk, tail);
-
-		kernel_neon_begin();
 	}
 
-	if (walk->nbytes) {
-		sm4_ce_ccm_crypt(rkey_enc, walk->dst.virt.addr,
-				 walk->src.virt.addr, walk->iv,
-				 walk->nbytes, mac);
-
-		sm4_ce_ccm_final(rkey_enc, ctr0, mac);
+	sm4_ce_ccm_final(rkey_enc, ctr0, mac);
 
-		kernel_neon_end();
-
-		err = skcipher_walk_done(walk, 0);
-	} else {
-		sm4_ce_ccm_final(rkey_enc, ctr0, mac);
-
-		kernel_neon_end();
-	}
+	kernel_neon_end();
 
 	return err;
 }
-- 
2.51.0.710.ga91ca5db03-goog