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

Ard Biesheuvel
2025-10-08T15:46:48Z

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