target/linux/ipq40xx/patches-4.19/048-crypto-qce-use-AES-fallback-for-small-requests.patch

   1 From 2d3b6fae7d1a2ad821769440daa91d7eec5c8250 Mon Sep 17 00:00:00 2001
   2 From: Eneas U de Queiroz <cotequeiroz@gmail.com>
   3 Date: Fri, 20 Dec 2019 09:41:44 -0300
   4 Subject: [PATCH] crypto: qce - use AES fallback for small requests
   5
   6 Process small blocks using the fallback cipher, as a workaround for an
   7 observed failure (DMA-related, apparently) when computing the GCM ghash
   8 key.  This brings a speed gain as well, since it avoids the latency of
   9 using the hardware engine to process small blocks.
  10
  11 Using software for all 16-byte requests would be enough to make GCM
  12 work, but to increase performance, a larger threshold would be better.
  13 Measuring the performance of supported ciphers with openssl speed,
  14 software matches hardware at around 768-1024 bytes.
  15
  16 Considering the 256-bit ciphers, software is 2-3 times faster than qce
  17 at 256-bytes, 30% faster at 512, and about even at 768-bytes.  With
  18 128-bit keys, the break-even point would be around 1024-bytes.
  19
  20 This adds the 'aes_sw_max_len' parameter, to set the largest request
  21 length processed by the software fallback.  Its default is being set to
  22 512 bytes, a little lower than the break-even point, to balance the cost
  23 in CPU usage.
  24
  25 Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>
  26
  27 --- a/drivers/crypto/Kconfig
  28 +++ b/drivers/crypto/Kconfig
  29 @@ -585,6 +585,29 @@ config CRYPTO_DEV_QCE
  30           hardware. To compile this driver as a module, choose M here. The
  31           module will be called qcrypto.
  32
  33 +config CRYPTO_DEV_QCE_SW_MAX_LEN
  34 +       int "Default maximum request size to use software for AES"
  35 +       depends on CRYPTO_DEV_QCE && CRYPTO_DEV_QCE_SKCIPHER
  36 +       default 512
  37 +       help
  38 +         This sets the default maximum request size to perform AES requests
  39 +         using software instead of the crypto engine.  It can be changed by
  40 +         setting the aes_sw_max_len parameter.
  41 +
  42 +         Small blocks are processed faster in software than hardware.
  43 +         Considering the 256-bit ciphers, software is 2-3 times faster than
  44 +         qce at 256-bytes, 30% faster at 512, and about even at 768-bytes.
  45 +         With 128-bit keys, the break-even point would be around 1024-bytes.
  46 +
  47 +         The default is set a little lower, to 512 bytes, to balance the
  48 +         cost in CPU usage.  The minimum recommended setting is 16-bytes
  49 +         (1 AES block), since AES-GCM will fail if you set it lower.
  50 +         Setting this to zero will send all requests to the hardware.
  51 +
  52 +         Note that 192-bit keys are not supported by the hardware and are
  53 +         always processed by the software fallback, and all DES requests
  54 +         are done by the hardware.
  55 +
  56  config CRYPTO_DEV_QCOM_RNG
  57         tristate "Qualcomm Random Number Generator Driver"
  58         depends on ARCH_QCOM || COMPILE_TEST
  59 --- a/drivers/crypto/qce/skcipher.c
  60 +++ b/drivers/crypto/qce/skcipher.c
  61 @@ -13,6 +13,7 @@
  62
  63  #include <linux/device.h>
  64  #include <linux/interrupt.h>
  65 +#include <linux/moduleparam.h>
  66  #include <linux/types.h>
  67  #include <crypto/aes.h>
  68  #include <crypto/des.h>
  69 @@ -20,6 +21,13 @@
  70
  71  #include "cipher.h"
  72
  73 +static unsigned int aes_sw_max_len = CONFIG_CRYPTO_DEV_QCE_SW_MAX_LEN;
  74 +module_param(aes_sw_max_len, uint, 0644);
  75 +MODULE_PARM_DESC(aes_sw_max_len,
  76 +                "Only use hardware for AES requests larger than this "
  77 +                "[0=always use hardware; anything <16 breaks AES-GCM; default="
  78 +                __stringify(CONFIG_CRYPTO_DEV_QCE_SOFT_THRESHOLD)"]");
  79 +
  80  static LIST_HEAD(skcipher_algs);
  81
  82  static void qce_skcipher_done(void *data)
  83 @@ -170,15 +178,7 @@ static int qce_skcipher_setkey(struct cr
  84         if (!key || !keylen)
  85                 return -EINVAL;
  86
  87 -       if (IS_AES(flags)) {
  88 -               switch (IS_XTS(flags) ? keylen >> 1 : keylen) {
  89 -               case AES_KEYSIZE_128:
  90 -               case AES_KEYSIZE_256:
  91 -                       break;
  92 -               default:
  93 -                       goto fallback;
  94 -               }
  95 -       } else if (IS_DES(flags)) {
  96 +       if (IS_DES(flags)) {
  97                 u32 tmp[DES_EXPKEY_WORDS];
  98
  99                 ret = des_ekey(tmp, key);
 100 @@ -189,8 +189,8 @@ static int qce_skcipher_setkey(struct cr
 101
 102         ctx->enc_keylen = keylen;
 103         memcpy(ctx->enc_key, key, keylen);
 104 -       return 0;
 105 -fallback:
 106 +       if (!IS_AES(flags))
 107 +               return 0;
 108         ret = crypto_skcipher_setkey(ctx->fallback, key, keylen);
 109         if (!ret)
 110                 ctx->enc_keylen = keylen;
 111 @@ -213,8 +213,9 @@ static int qce_skcipher_crypt(struct skc
 112         rctx->flags |= encrypt ? QCE_ENCRYPT : QCE_DECRYPT;
 113         keylen = IS_XTS(rctx->flags) ? ctx->enc_keylen >> 1 : ctx->enc_keylen;
 114
 115 -       if (IS_AES(rctx->flags) && keylen != AES_KEYSIZE_128 &&
 116 -           keylen != AES_KEYSIZE_256) {
 117 +       if (IS_AES(rctx->flags) &&
 118 +           ((keylen != AES_KEYSIZE_128 && keylen != AES_KEYSIZE_256) ||
 119 +            req->cryptlen <= aes_sw_max_len)) {
 120                 SKCIPHER_REQUEST_ON_STACK(subreq, ctx->fallback);
 121
 122                 skcipher_request_set_tfm(subreq, ctx->fallback);