[PATCH v3 03/21] crypto/arm64: sm4-ce-gcm - Avoid pointless yield of the NEON unit

Ard Biesheuvel
2025-10-08T15:46:49Z

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().

While at it, simplify the logic.

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

diff --git a/arch/arm64/crypto/sm4-ce-gcm-glue.c b/arch/arm64/crypto/sm4-ce-gcm-glue.c
index c2ea3d5f690b..8f6fc8c33c3f 100644
--- a/arch/arm64/crypto/sm4-ce-gcm-glue.c
+++ b/arch/arm64/crypto/sm4-ce-gcm-glue.c
@@ -154,36 +154,23 @@ static int gcm_crypt(struct aead_request *req, struct skcipher_walk *walk,
if (req->assoclen)
gcm_calculate_auth_mac(req, ghash);

- while (walk->nbytes) {
+ do {
unsigned int tail = walk->nbytes % SM4_BLOCK_SIZE;
const u8 *src = walk->src.virt.addr;
u8 *dst = walk->dst.virt.addr;
+ const u8 *l = NULL;

if (walk->nbytes == walk->total) {
- sm4_ce_pmull_gcm_crypt(ctx->key.rkey_enc, dst, src, iv,
- walk->nbytes, ghash,
- ctx->ghash_table,
- (const u8 *)&lengths);
-
- kernel_neon_end();
-
- return skcipher_walk_done(walk, 0);
+ l = (const u8 *)&lengths;
+ tail = 0;
}

sm4_ce_pmull_gcm_crypt(ctx->key.rkey_enc, dst, src, iv,
walk->nbytes - tail, ghash,
- ctx->ghash_table, NULL);
-
- kernel_neon_end();
+ ctx->ghash_table, l);

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);
+ } while (walk->nbytes);

kernel_neon_end();

--
2.51.0.710.ga91ca5db03-goog