CBC encryption is strictly sequential, and so the current AES code
simply processes the input one block at a time. However, we are
about to add yield support, which adds a bit of overhead, and which
we prefer to align with other modes in terms of granularity (i.e.,
it is better to have all routines yield every 64 bytes and not have
an exception for CBC encrypt which yields every 16 bytes)
So unroll the loop by 4. We still cannot perform the AES algorithm in
parallel, but we can at least merge the loads and stores.
Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
---
arch/arm64/crypto/aes-modes.S | 31 ++++++++++++++++----
1 file changed, 25 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/crypto/aes-modes.S b/arch/arm64/crypto/aes-modes.S
index 27a235b2ddee..e86535a1329d 100644
--- a/arch/arm64/crypto/aes-modes.S
+++ b/arch/arm64/crypto/aes-modes.S
@@ -94,17 +94,36 @@ AES_ENDPROC(aes_ecb_decrypt)
*/
AES_ENTRY(aes_cbc_encrypt)
- ld1 {v0.16b}, [x5] /* get iv */
+ ld1 {v4.16b}, [x5] /* get iv */
enc_prepare w3, x2, x6
-.Lcbcencloop:
- ld1 {v1.16b}, [x1], #16 /* get next pt block */
- eor v0.16b, v0.16b, v1.16b /* ..and xor with iv */
+.Lcbcencloop4x:
+ subs w4, w4, #4
+ bmi .Lcbcenc1x
+ ld1 {v0.16b-v3.16b}, [x1], #64 /* get 4 pt blocks */
+ eor v0.16b, v0.16b, v4.16b /* ..and xor with iv */
encrypt_block v0, w3, x2, x6, w7
- st1 {v0.16b}, [x0], #16
+ eor v1.16b, v1.16b, v0.16b
+ encrypt_block v1, w3, x2, x6, w7
+ eor v2.16b, v2.16b, v1.16b
+ encrypt_block v2, w3, x2, x6, w7
+ eor v3.16b, v3.16b, v2.16b
+ encrypt_block v3, w3, x2, x6, w7
+ st1 {v0.16b-v3.16b}, [x0], #64
+ mov v4.16b, v3.16b
+ b .Lcbcencloop4x
+.Lcbcenc1x:
+ adds w4, w4, #4
+ beq .Lcbcencout
+.Lcbcencloop:
+ ld1 {v0.16b}, [x1], #16 /* get next pt block */
+ eor v4.16b, v4.16b, v0.16b /* ..and xor with iv */
+ encrypt_block v4, w3, x2, x6, w7
+ st1 {v4.16b}, [x0], #16
subs w4, w4, #1
bne .Lcbcencloop
- st1 {v0.16b}, [x5] /* return iv */
+.Lcbcencout:
+ st1 {v4.16b}, [x5] /* return iv */
ret
AES_ENDPROC(aes_cbc_encrypt)
--
2.15.1
