[PATCH 3/5] crypto/arm64: sm4-ce-gcm - 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().

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/crypto/sm4-ce-gcm-glue.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/crypto/sm4-ce-gcm-glue.c b/arch/arm64/crypto/sm4-ce-gcm-glue.c
index c2ea3d5f690b..170cd0151385 100644
--- a/arch/arm64/crypto/sm4-ce-gcm-glue.c
+++ b/arch/arm64/crypto/sm4-ce-gcm-glue.c
@@ -165,26 +165,22 @@ static int gcm_crypt(struct aead_request *req, struct skcipher_walk *walk,
 					       ctx->ghash_table,
 					       (const u8 *)&lengths);
 
-			kernel_neon_end();
-
-			return skcipher_walk_done(walk, 0);
+			err = skcipher_walk_done(walk, 0);
+			goto out;
 		}
 
 		sm4_ce_pmull_gcm_crypt(ctx->key.rkey_enc, dst, src, iv,
 				       walk->nbytes - tail, ghash,
 				       ctx->ghash_table, NULL);
 
-		kernel_neon_end();
-
 		err = skcipher_walk_done(walk, tail);
-
-		kernel_neon_begin();
 	}
 
 	sm4_ce_pmull_gcm_crypt(ctx->key.rkey_enc, NULL, NULL, iv,
 			       walk->nbytes, ghash, ctx->ghash_table,
 			       (const u8 *)&lengths);
 
+out:
 	kernel_neon_end();
 
 	return err;
-- 
2.51.0.384.g4c02a37b29-goog