crypto: drbg - eliminate constant reinitialization of SGL

The CTR DRBG requires two SGLs pointing to input/output buffers for the
CTR AES operation. The used SGLs always have only one entry. Thus, the
SGL can be initialized during allocation time, preventing a
re-initialization of the SGLs during each call.

The performance is increased by about 1 to 3 percent depending on the
size of the requested buffer size.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/crypto/drbg.h b/include/crypto/drbg.h
index 8f941102af36..54b9f5d375f5 100644
--- a/include/crypto/drbg.h
+++ b/include/crypto/drbg.h
@@ -127,6 +127,7 @@ struct drbg_state {
         __u8 *outscratchpadbuf;                 /* CTR mode output scratchpad */
         __u8 *outscratchpad;                    /* CTR mode aligned outbuf */
         struct crypto_wait ctr_wait;            /* CTR mode async wait obj */
+        struct scatterlist sg_in, sg_out;       /* CTR mode SGLs */
 
         bool seeded;            /* DRBG fully seeded? */
         bool pr;                /* Prediction resistance enabled? */