summaryrefslogtreecommitdiff
path: root/drivers/crypto/Kconfig
diff options
context:
space:
mode:
authorEneas U de Queiroz <cotequeiroz@gmail.com>2020-02-07 18:02:26 +0300
committerHerbert Xu <herbert@gondor.apana.org.au>2020-02-13 12:05:27 +0300
commitce163ba0bf298f1707321ac025ef639f88e62801 (patch)
tree0d5548b88ef4c1cecf98435d66893d6770e17836 /drivers/crypto/Kconfig
parentd6364b8128439a8c0e381f80c38667de9f15eef8 (diff)
downloadlinux-ce163ba0bf298f1707321ac025ef639f88e62801.tar.xz
crypto: qce - use AES fallback for small requests
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@gmail.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'drivers/crypto/Kconfig')
-rw-r--r--drivers/crypto/Kconfig23
1 files changed, 23 insertions, 0 deletions
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