Process small blocks using the fallback cipher, as a workaround for an
observed failure (DMA-related, apparently) when computing the GCM ghash
key. This brings a speed gain as well, since it avoids the latency of
using the hardware engine to process small blocks.
Using software for all 16-byte requests would be enough to make GCM
work, but to increase performance, a larger threshold would be better.
Measuring the performance of supported ciphers with openssl speed,
software matches hardware at around 768-1024 bytes.
Considering the 256-bit ciphers, software is 2-3 times faster than qce
at 256-bytes, 30% faster at 512, and about even at 768-bytes. With
128-bit keys, the break-even point would be around 1024-bytes.
This adds the 'aes_sw_max_len' parameter, to set the largest request
length processed by the software fallback. Its default is being set to
512 bytes, a little lower than the break-even point, to balance the cost
in CPU usage.
Signed-off-by: Eneas U de Queiroz <cotequeiroz@xxxxxxxxx>
diff --git a/drivers/crypto/Kconfig b/drivers/crypto/Kconfig
index c2767ed54dfe..052d3ff7fb20 100644
--- a/drivers/crypto/Kconfig
+++ b/drivers/crypto/Kconfig
@@ -685,6 +685,29 @@ choice
endchoice
+config CRYPTO_DEV_QCE_SW_MAX_LEN
+ int "Default maximum request size to use software for AES"
+ depends on CRYPTO_DEV_QCE && CRYPTO_DEV_QCE_SKCIPHER
+ default 512
+ help
+ This sets the default maximum request size to perform AES requests
+ using software instead of the crypto engine. It can be changed by
+ setting the aes_sw_max_len parameter.
+
+ Small blocks are processed faster in software than hardware.
+ Considering the 256-bit ciphers, software is 2-3 times faster than
+ qce at 256-bytes, 30% faster at 512, and about even at 768-bytes.
+ With 128-bit keys, the break-even point would be around 1024-bytes.
+
+ The default is set a little lower, to 512 bytes, to balance the
+ cost in CPU usage. The minimum recommended setting is 16-bytes
+ (1 AES block), since AES-GCM will fail if you set it lower.
+ Setting this to zero will send all requests to the hardware.
+
+ Note that 192-bit keys are not supported by the hardware and are
+ always processed by the software fallback, and all DES requests
+ are done by the hardware.
+
config CRYPTO_DEV_QCOM_RNG
tristate "Qualcomm Random Number Generator Driver"
depends on ARCH_QCOM || COMPILE_TEST
diff --git a/drivers/crypto/qce/skcipher.c b/drivers/crypto/qce/skcipher.c
index 63ae75809cb7..a3536495b6b0 100644
--- a/drivers/crypto/qce/skcipher.c
+++ b/drivers/crypto/qce/skcipher.c
@@ -5,6 +5,7 @@
#include <linux/device.h>
#include <linux/interrupt.h>
+#include <linux/moduleparam.h>
#include <linux/types.h>
#include <crypto/aes.h>
#include <crypto/internal/des.h>
@@ -12,6 +13,13 @@
#include "cipher.h"
+unsigned int aes_sw_max_len = CONFIG_CRYPTO_DEV_QCE_SW_MAX_LEN;
+module_param(aes_sw_max_len, uint, 0644);
+MODULE_PARM_DESC(aes_sw_max_len,
+ "Only use hardware for AES requests larger than this "
+ "[0=always use hardware; anything <16 breaks AES-GCM; default="
+ __stringify(CONFIG_CRYPTO_DEV_QCE_SOFT_THRESHOLD) "]");
+
static LIST_HEAD(skcipher_algs);
static void qce_skcipher_done(void *data)
@@ -166,15 +174,10 @@ static int qce_skcipher_setkey(struct crypto_skcipher *ablk, const u8 *key,
switch (IS_XTS(flags) ? keylen >> 1 : keylen) {
case AES_KEYSIZE_128:
case AES_KEYSIZE_256:
+ memcpy(ctx->enc_key, key, keylen);
break;
- default:
- goto fallback;
}
- ctx->enc_keylen = keylen;
- memcpy(ctx->enc_key, key, keylen);
- return 0;
-fallback:
ret = crypto_sync_skcipher_setkey(ctx->fallback, key, keylen);
if (!ret)
ctx->enc_keylen = keylen;
@@ -224,8 +227,9 @@ static int qce_skcipher_crypt(struct skcipher_request *req, int encrypt)
rctx->flags |= encrypt ? QCE_ENCRYPT : QCE_DECRYPT;
keylen = IS_XTS(rctx->flags) ? ctx->enc_keylen >> 1 : ctx->enc_keylen;
- if (IS_AES(rctx->flags) && keylen != AES_KEYSIZE_128 &&
- keylen != AES_KEYSIZE_256) {
+ if (IS_AES(rctx->flags) &&
+ ((keylen != AES_KEYSIZE_128 && keylen != AES_KEYSIZE_256)
+ || req->cryptlen <= aes_sw_max_len)) {
SYNC_SKCIPHER_REQUEST_ON_STACK(subreq, ctx->fallback);
skcipher_request_set_sync_tfm(subreq, ctx->fallback);
