s390/crypto: add SIMD implementation for ChaCha20

Add an implementation of the ChaCha20 stream cipher (see e.g. RFC 7539)
that makes use of z13's vector instruction set extension.

The original implementation is by Andy Polyakov which is
adapted for kernel use.

Four to six blocks are processed in parallel resulting in a performance
gain for inputs >= 256 bytes.

chacha20-generic

1 operation in 622 cycles (256 bytes)
1 operation in 2346 cycles (1024 bytes)

chacha20-s390

1 operation in 218 cycles (256 bytes)
1 operation in 647 cycles (1024 bytes)

Cc: Andy Polyakov <appro@openssl.org>
Reviewed-by: Harald Freudenberger <freude@de.ibm.com>
Signed-off-by: Patrick Steuer <patrick.steuer@de.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/configs/debug_defconfig

@@ -768,6 +768,7 @@ CONFIG_CRYPTO_SHA3_256_S390=m
 CONFIG_CRYPTO_SHA3_512_S390=m
 CONFIG_CRYPTO_DES_S390=m
 CONFIG_CRYPTO_AES_S390=m
+CONFIG_CRYPTO_CHACHA_S390=m
 CONFIG_CRYPTO_GHASH_S390=m
 CONFIG_CRYPTO_CRC32_S390=y
 CONFIG_CRYPTO_DEV_VIRTIO=m

arch/s390/configs/defconfig

@@ -755,6 +755,7 @@ CONFIG_CRYPTO_SHA3_256_S390=m
 CONFIG_CRYPTO_SHA3_512_S390=m
 CONFIG_CRYPTO_DES_S390=m
 CONFIG_CRYPTO_AES_S390=m
+CONFIG_CRYPTO_CHACHA_S390=m
 CONFIG_CRYPTO_GHASH_S390=m
 CONFIG_CRYPTO_CRC32_S390=y
 CONFIG_CRYPTO_DEV_VIRTIO=m

arch/s390/crypto/Makefile

@@ -11,9 +11,11 @@ obj-$(CONFIG_CRYPTO_SHA3_512_S390) += sha3_512_s390.o sha_common.o
 obj-$(CONFIG_CRYPTO_DES_S390) += des_s390.o
 obj-$(CONFIG_CRYPTO_AES_S390) += aes_s390.o
 obj-$(CONFIG_CRYPTO_PAES_S390) += paes_s390.o
+obj-$(CONFIG_CRYPTO_CHACHA_S390) += chacha_s390.o
 obj-$(CONFIG_S390_PRNG) += prng.o
 obj-$(CONFIG_CRYPTO_GHASH_S390) += ghash_s390.o
 obj-$(CONFIG_CRYPTO_CRC32_S390) += crc32-vx_s390.o
 obj-$(CONFIG_ARCH_RANDOM) += arch_random.o
 
 crc32-vx_s390-y := crc32-vx.o crc32le-vx.o crc32be-vx.o
+chacha_s390-y := chacha-glue.o chacha-s390.o

arch/s390/crypto/chacha-glue.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * s390 ChaCha stream cipher.
+ *
+ * Copyright IBM Corp. 2021
+ */
+
+#define KMSG_COMPONENT "chacha_s390"
+#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
+
+#include <crypto/internal/chacha.h>
+#include <crypto/internal/skcipher.h>
+#include <crypto/algapi.h>
+#include <linux/cpufeature.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sizes.h>
+#include <asm/fpu/api.h>
+#include "chacha-s390.h"
+
+static void chacha20_crypt_s390(u32 *state, u8 *dst, const u8 *src,
+				unsigned int nbytes, const u32 *key,
+				u32 *counter)
+{
+	struct kernel_fpu vxstate;
+
+	kernel_fpu_begin(&vxstate, KERNEL_VXR);
+	chacha20_vx(dst, src, nbytes, key, counter);
+	kernel_fpu_end(&vxstate, KERNEL_VXR);
+
+	*counter += round_up(nbytes, CHACHA_BLOCK_SIZE) / CHACHA_BLOCK_SIZE;
+}
+
+static int chacha20_s390(struct skcipher_request *req)
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+	struct chacha_ctx *ctx = crypto_skcipher_ctx(tfm);
+	u32 state[CHACHA_STATE_WORDS] __aligned(16);
+	struct skcipher_walk walk;
+	unsigned int nbytes;
+	int rc;
+
+	rc = skcipher_walk_virt(&walk, req, false);
+	chacha_init_generic(state, ctx->key, req->iv);
+
+	while (walk.nbytes > 0) {
+		nbytes = walk.nbytes;
+		if (nbytes < walk.total)
+			nbytes = round_down(nbytes, walk.stride);
+
+		if (nbytes <= CHACHA_BLOCK_SIZE) {
+			chacha_crypt_generic(state, walk.dst.virt.addr,
+					     walk.src.virt.addr, nbytes,
+					     ctx->nrounds);
+		} else {
+			chacha20_crypt_s390(state, walk.dst.virt.addr,
+					    walk.src.virt.addr, nbytes,
+					    &state[4], &state[12]);
+		}
+		rc = skcipher_walk_done(&walk, walk.nbytes - nbytes);
+	}
+	return rc;
+}
+
+static struct skcipher_alg chacha_algs[] = {
+	{
+		.base.cra_name		= "chacha20",
+		.base.cra_driver_name	= "chacha20-s390",
+		.base.cra_priority	= 900,
+		.base.cra_blocksize	= 1,
+		.base.cra_ctxsize	= sizeof(struct chacha_ctx),
+		.base.cra_module	= THIS_MODULE,
+
+		.min_keysize		= CHACHA_KEY_SIZE,
+		.max_keysize		= CHACHA_KEY_SIZE,
+		.ivsize			= CHACHA_IV_SIZE,
+		.chunksize		= CHACHA_BLOCK_SIZE,
+		.setkey			= chacha20_setkey,
+		.encrypt		= chacha20_s390,
+		.decrypt		= chacha20_s390,
+	}
+};
+
+static int __init chacha_mod_init(void)
+{
+	return crypto_register_skciphers(chacha_algs, ARRAY_SIZE(chacha_algs));
+}
+
+static void __exit chacha_mod_fini(void)
+{
+	crypto_unregister_skciphers(chacha_algs, ARRAY_SIZE(chacha_algs));
+}
+
+module_cpu_feature_match(VXRS, chacha_mod_init);
+module_exit(chacha_mod_fini);
+
+MODULE_DESCRIPTION("ChaCha20 stream cipher");
+MODULE_LICENSE("GPL v2");
+
+MODULE_ALIAS_CRYPTO("chacha20");

arch/s390/crypto/chacha-s390.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * s390 ChaCha stream cipher.
+ *
+ * Copyright IBM Corp. 2021
+ */
+
+#ifndef _CHACHA_S390_H
+#define _CHACHA_S390_H
+
+void chacha20_vx(u8 *out, const u8 *inp, size_t len, const u32 *key,
+		 const u32 *counter);
+
+#endif /* _CHACHA_S390_H */

arch/s390/include/asm/vx-insn.h

@@ -372,6 +372,16 @@
 	MRXBOPC	\hint, 0x36, v1, v3
 .endm
 
+/* VECTOR STORE */
+.macro	VST	vr1, disp, index="%r0", base
+	VX_NUM	v1, \vr1
+	GR_NUM	x2, \index
+	GR_NUM	b2, \base	    /* Base register */
+	.word	0xE700 | ((v1&15) << 4) | (x2&15)
+	.word	(b2 << 12) | (\disp)
+	MRXBOPC	0, 0x0E, v1
+.endm
+
 /* VECTOR STORE MULTIPLE */
 .macro	VSTM	vfrom, vto, disp, base, hint=3
 	VX_NUM	v1, \vfrom
@@ -411,6 +421,81 @@
 	VUPLL	\vr1, \vr2, 2
 .endm
 
+/* VECTOR PERMUTE DOUBLEWORD IMMEDIATE */
+.macro	VPDI	vr1, vr2, vr3, m4
+	VX_NUM	v1, \vr1
+	VX_NUM	v2, \vr2
+	VX_NUM	v3, \vr3
+	.word	0xE700 | ((v1&15) << 4) | (v2&15)
+	.word	((v3&15) << 12)
+	MRXBOPC	\m4, 0x84, v1, v2, v3
+.endm
+
+/* VECTOR REPLICATE */
+.macro	VREP	vr1, vr3, imm2, m4
+	VX_NUM	v1, \vr1
+	VX_NUM	v3, \vr3
+	.word	0xE700 | ((v1&15) << 4) | (v3&15)
+	.word	\imm2
+	MRXBOPC	\m4, 0x4D, v1, v3
+.endm
+.macro	VREPB	vr1, vr3, imm2
+	VREP	\vr1, \vr3, \imm2, 0
+.endm
+.macro	VREPH	vr1, vr3, imm2
+	VREP	\vr1, \vr3, \imm2, 1
+.endm
+.macro	VREPF	vr1, vr3, imm2
+	VREP	\vr1, \vr3, \imm2, 2
+.endm
+.macro	VREPG	vr1, vr3, imm2
+	VREP	\vr1, \vr3, \imm2, 3
+.endm
+
+/* VECTOR MERGE HIGH */
+.macro	VMRH	vr1, vr2, vr3, m4
+	VX_NUM	v1, \vr1
+	VX_NUM	v2, \vr2
+	VX_NUM	v3, \vr3
+	.word	0xE700 | ((v1&15) << 4) | (v2&15)
+	.word	((v3&15) << 12)
+	MRXBOPC	\m4, 0x61, v1, v2, v3
+.endm
+.macro	VMRHB	vr1, vr2, vr3
+	VMRH	\vr1, \vr2, \vr3, 0
+.endm
+.macro	VMRHH	vr1, vr2, vr3
+	VMRH	\vr1, \vr2, \vr3, 1
+.endm
+.macro	VMRHF	vr1, vr2, vr3
+	VMRH	\vr1, \vr2, \vr3, 2
+.endm
+.macro	VMRHG	vr1, vr2, vr3
+	VMRH	\vr1, \vr2, \vr3, 3
+.endm
+
+/* VECTOR MERGE LOW */
+.macro	VMRL	vr1, vr2, vr3, m4
+	VX_NUM	v1, \vr1
+	VX_NUM	v2, \vr2
+	VX_NUM	v3, \vr3
+	.word	0xE700 | ((v1&15) << 4) | (v2&15)
+	.word	((v3&15) << 12)
+	MRXBOPC	\m4, 0x60, v1, v2, v3
+.endm
+.macro	VMRLB	vr1, vr2, vr3
+	VMRL	\vr1, \vr2, \vr3, 0
+.endm
+.macro	VMRLH	vr1, vr2, vr3
+	VMRL	\vr1, \vr2, \vr3, 1
+.endm
+.macro	VMRLF	vr1, vr2, vr3
+	VMRL	\vr1, \vr2, \vr3, 2
+.endm
+.macro	VMRLG	vr1, vr2, vr3
+	VMRL	\vr1, \vr2, \vr3, 3
+.endm
+
 
 /* Vector integer instructions */
 
@@ -557,5 +642,37 @@
 	VESRAV	\vr1, \vr2, \vr3, 3
 .endm
 
+/* VECTOR ELEMENT ROTATE LEFT LOGICAL */
+.macro	VERLL	vr1, vr3, disp, base="%r0", m4
+	VX_NUM	v1, \vr1
+	VX_NUM	v3, \vr3
+	GR_NUM	b2, \base
+	.word	0xE700 | ((v1&15) << 4) | (v3&15)
+	.word	(b2 << 12) | (\disp)
+	MRXBOPC	\m4, 0x33, v1, v3
+.endm
+.macro	VERLLB	vr1, vr3, disp, base="%r0"
+	VERLL	\vr1, \vr3, \disp, \base, 0
+.endm
+.macro	VERLLH	vr1, vr3, disp, base="%r0"
+	VERLL	\vr1, \vr3, \disp, \base, 1
+.endm
+.macro	VERLLF	vr1, vr3, disp, base="%r0"
+	VERLL	\vr1, \vr3, \disp, \base, 2
+.endm
+.macro	VERLLG	vr1, vr3, disp, base="%r0"
+	VERLL	\vr1, \vr3, \disp, \base, 3
+.endm
+
+/* VECTOR SHIFT LEFT DOUBLE BY BYTE */
+.macro	VSLDB	vr1, vr2, vr3, imm4
+	VX_NUM	v1, \vr1
+	VX_NUM	v2, \vr2
+	VX_NUM	v3, \vr3
+	.word	0xE700 | ((v1&15) << 4) | (v2&15)
+	.word	((v3&15) << 12) | (\imm4)
+	MRXBOPC	0, 0x77, v1, v2, v3
+.endm
+
 #endif	/* __ASSEMBLY__ */
 #endif	/* __ASM_S390_VX_INSN_H */

drivers/crypto/Kconfig

@@ -213,6 +213,18 @@ config CRYPTO_AES_S390
 	  key sizes and XTS mode is hardware accelerated for 256 and
 	  512 bit keys.
 
+config CRYPTO_CHACHA_S390
+	tristate "ChaCha20 stream cipher"
+	depends on S390
+	select CRYPTO_ALGAPI
+	select CRYPTO_SKCIPHER
+	select CRYPTO_CHACHA20
+	help
+	  This is the s390 SIMD implementation of the ChaCha20 stream
+	  cipher (RFC 7539).
+
+	  It is available as of z13.
+
 config S390_PRNG
 	tristate "Pseudo random number generator device driver"
 	depends on S390