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123 lines
4.5 KiB
Diff
123 lines
4.5 KiB
Diff
From 2d3b6fae7d1a2ad821769440daa91d7eec5c8250 Mon Sep 17 00:00:00 2001
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From: Eneas U de Queiroz <cotequeiroz@gmail.com>
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Date: Fri, 20 Dec 2019 09:41:44 -0300
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Subject: [PATCH] crypto: qce - use AES fallback for small requests
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Process small blocks using the fallback cipher, as a workaround for an
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observed failure (DMA-related, apparently) when computing the GCM ghash
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key. This brings a speed gain as well, since it avoids the latency of
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using the hardware engine to process small blocks.
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Using software for all 16-byte requests would be enough to make GCM
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work, but to increase performance, a larger threshold would be better.
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Measuring the performance of supported ciphers with openssl speed,
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software matches hardware at around 768-1024 bytes.
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Considering the 256-bit ciphers, software is 2-3 times faster than qce
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at 256-bytes, 30% faster at 512, and about even at 768-bytes. With
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128-bit keys, the break-even point would be around 1024-bytes.
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This adds the 'aes_sw_max_len' parameter, to set the largest request
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length processed by the software fallback. Its default is being set to
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512 bytes, a little lower than the break-even point, to balance the cost
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in CPU usage.
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Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>
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--- a/drivers/crypto/Kconfig
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+++ b/drivers/crypto/Kconfig
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@@ -585,6 +585,29 @@ config CRYPTO_DEV_QCE
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hardware. To compile this driver as a module, choose M here. The
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module will be called qcrypto.
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+config CRYPTO_DEV_QCE_SW_MAX_LEN
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+ int "Default maximum request size to use software for AES"
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+ depends on CRYPTO_DEV_QCE && CRYPTO_DEV_QCE_SKCIPHER
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+ default 512
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+ help
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+ This sets the default maximum request size to perform AES requests
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+ using software instead of the crypto engine. It can be changed by
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+ setting the aes_sw_max_len parameter.
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+
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+ Small blocks are processed faster in software than hardware.
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+ Considering the 256-bit ciphers, software is 2-3 times faster than
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+ qce at 256-bytes, 30% faster at 512, and about even at 768-bytes.
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+ With 128-bit keys, the break-even point would be around 1024-bytes.
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+
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+ The default is set a little lower, to 512 bytes, to balance the
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+ cost in CPU usage. The minimum recommended setting is 16-bytes
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+ (1 AES block), since AES-GCM will fail if you set it lower.
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+ Setting this to zero will send all requests to the hardware.
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+
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+ Note that 192-bit keys are not supported by the hardware and are
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+ always processed by the software fallback, and all DES requests
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+ are done by the hardware.
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+
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config CRYPTO_DEV_QCOM_RNG
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tristate "Qualcomm Random Number Generator Driver"
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depends on ARCH_QCOM || COMPILE_TEST
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--- a/drivers/crypto/qce/skcipher.c
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+++ b/drivers/crypto/qce/skcipher.c
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@@ -13,6 +13,7 @@
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#include <linux/device.h>
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#include <linux/interrupt.h>
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+#include <linux/moduleparam.h>
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#include <linux/types.h>
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#include <crypto/aes.h>
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#include <crypto/des.h>
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@@ -20,6 +21,13 @@
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#include "cipher.h"
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+static unsigned int aes_sw_max_len = CONFIG_CRYPTO_DEV_QCE_SW_MAX_LEN;
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+module_param(aes_sw_max_len, uint, 0644);
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+MODULE_PARM_DESC(aes_sw_max_len,
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+ "Only use hardware for AES requests larger than this "
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+ "[0=always use hardware; anything <16 breaks AES-GCM; default="
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+ __stringify(CONFIG_CRYPTO_DEV_QCE_SOFT_THRESHOLD)"]");
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+
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static LIST_HEAD(skcipher_algs);
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static void qce_skcipher_done(void *data)
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@@ -170,15 +178,7 @@ static int qce_skcipher_setkey(struct cr
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if (!key || !keylen)
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return -EINVAL;
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- if (IS_AES(flags)) {
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- switch (IS_XTS(flags) ? keylen >> 1 : keylen) {
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- case AES_KEYSIZE_128:
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- case AES_KEYSIZE_256:
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- break;
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- default:
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- goto fallback;
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- }
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- } else if (IS_DES(flags)) {
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+ if (IS_DES(flags)) {
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u32 tmp[DES_EXPKEY_WORDS];
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ret = des_ekey(tmp, key);
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@@ -189,8 +189,8 @@ static int qce_skcipher_setkey(struct cr
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ctx->enc_keylen = keylen;
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memcpy(ctx->enc_key, key, keylen);
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- return 0;
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-fallback:
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+ if (!IS_AES(flags))
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+ return 0;
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ret = crypto_skcipher_setkey(ctx->fallback, key, keylen);
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if (!ret)
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ctx->enc_keylen = keylen;
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@@ -213,8 +213,9 @@ static int qce_skcipher_crypt(struct skc
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rctx->flags |= encrypt ? QCE_ENCRYPT : QCE_DECRYPT;
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keylen = IS_XTS(rctx->flags) ? ctx->enc_keylen >> 1 : ctx->enc_keylen;
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- if (IS_AES(rctx->flags) && keylen != AES_KEYSIZE_128 &&
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- keylen != AES_KEYSIZE_256) {
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+ if (IS_AES(rctx->flags) &&
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+ ((keylen != AES_KEYSIZE_128 && keylen != AES_KEYSIZE_256) ||
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+ req->cryptlen <= aes_sw_max_len)) {
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SKCIPHER_REQUEST_ON_STACK(subreq, ctx->fallback);
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skcipher_request_set_tfm(subreq, ctx->fallback);
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