Subject: [PATCH v2 3/3] crypto: arm64/crct10dif-ce - cleanup and optimizations

From: Eric Biggers <[email-masked]>
Date: Tue, 29 Jan 2019 00:00:29 -0800

From: Eric Biggers <[email-masked]>

The x86, arm, and arm64 asm implementations of crct10dif are very
difficult to understand partly because many of the comments, labels, and
macros are named incorrectly: the lengths mentioned are usually off by a
factor of two from the actual code.  Many other things are unnecessarily
convoluted as well, e.g. there are many more fold constants than
actually needed and some aren't fully reduced.

This series therefore cleans up all these implementations to be much
more maintainable.  I also made some small optimizations where I saw
opportunities, resulting in slightly better performance.

This patch cleans up the arm64 version.

Signed-off-by: Eric Biggers <[email-masked]>
---
 arch/arm64/crypto/crct10dif-ce-core.S | 496 ++++++++++++--------------
 arch/arm64/crypto/crct10dif-ce-glue.c |   4 +-
 2 files changed, 233 insertions(+), 267 deletions(-)

diff --git a/arch/arm64/crypto/crct10dif-ce-core.S b/arch/arm64/crypto/crct10dif-ce-core.S
index f7326259c40de..e545b42e6a468 100644
--- a/arch/arm64/crypto/crct10dif-ce-core.S
+++ b/arch/arm64/crypto/crct10dif-ce-core.S
@@ -2,12 +2,14 @@
 // Accelerated CRC-T10DIF using arm64 NEON and Crypto Extensions instructions
 //
 // Copyright (C) 2016 Linaro Ltd <[email-masked]>
+// Copyright (C) 2019 Google LLC <[email-masked]>
 //
 // This program is free software; you can redistribute it and/or modify
 // it under the terms of the GNU General Public License version 2 as
 // published by the Free Software Foundation.
 //
 
+// Derived from the x86 version:
 //
 // Implement fast CRC-T10DIF computation with SSE and PCLMULQDQ instructions
 //
@@ -54,19 +56,11 @@
 // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 //
-//       Function API:
-//       UINT16 crc_t10dif_pcl(
-//               UINT16 init_crc, //initial CRC value, 16 bits
-//               const unsigned char *buf, //buffer pointer to calculate CRC on
-//               UINT64 len //buffer length in bytes (64-bit data)
-//       );
-//
 //       Reference paper titled "Fast CRC Computation for Generic
 //	Polynomials Using PCLMULQDQ Instruction"
 //       URL: http://www.intel.com/content/dam/www/public/us/en/documents
 //  /white-papers/fast-crc-computation-generic-polynomials-pclmulqdq-paper.pdf
 //
-//
 
 #include <linux/linkage.h>
 #include <asm/assembler.h>
@@ -74,14 +68,14 @@
 	.text
 	.cpu		generic+crypto
 
-	arg1_low32	.req	w19
-	arg2		.req	x20
-	arg3		.req	x21
+	init_crc	.req	w19
+	buf		.req	x20
+	len		.req	x21
+	fold_consts_ptr	.req	x22
 
-	vzr		.req	v13
+	fold_consts	.req	v10
 
 	ad		.req	v14
-	bd		.req	v10
 
 	k00_16		.req	v15
 	k32_48		.req	v16
@@ -143,11 +137,11 @@ __pmull_p8_core:
 	ext		t5.8b, ad.8b, ad.8b, #2			// A2
 	ext		t6.8b, ad.8b, ad.8b, #3			// A3
 
-	pmull		t4.8h, t4.8b, bd.8b			// F = A1*B
+	pmull		t4.8h, t4.8b, fold_consts.8b		// F = A1*B
 	pmull		t8.8h, ad.8b, bd1.8b			// E = A*B1
-	pmull		t5.8h, t5.8b, bd.8b			// H = A2*B
+	pmull		t5.8h, t5.8b, fold_consts.8b		// H = A2*B
 	pmull		t7.8h, ad.8b, bd2.8b			// G = A*B2
-	pmull		t6.8h, t6.8b, bd.8b			// J = A3*B
+	pmull		t6.8h, t6.8b, fold_consts.8b		// J = A3*B
 	pmull		t9.8h, ad.8b, bd3.8b			// I = A*B3
 	pmull		t3.8h, ad.8b, bd4.8b			// K = A*B4
 	b		0f
@@ -157,11 +151,11 @@ __pmull_p8_core:
 	tbl		t5.16b, {ad.16b}, perm2.16b		// A2
 	tbl		t6.16b, {ad.16b}, perm3.16b		// A3
 
-	pmull2		t4.8h, t4.16b, bd.16b			// F = A1*B
+	pmull2		t4.8h, t4.16b, fold_consts.16b		// F = A1*B
 	pmull2		t8.8h, ad.16b, bd1.16b			// E = A*B1
-	pmull2		t5.8h, t5.16b, bd.16b			// H = A2*B
+	pmull2		t5.8h, t5.16b, fold_consts.16b		// H = A2*B
 	pmull2		t7.8h, ad.16b, bd2.16b			// G = A*B2
-	pmull2		t6.8h, t6.16b, bd.16b			// J = A3*B
+	pmull2		t6.8h, t6.16b, fold_consts.16b		// J = A3*B
 	pmull2		t9.8h, ad.16b, bd3.16b			// I = A*B3
 	pmull2		t3.8h, ad.16b, bd4.16b			// K = A*B4
 
@@ -203,14 +197,14 @@ __pmull_p8_core:
 ENDPROC(__pmull_p8_core)
 
 	.macro		__pmull_p8, rq, ad, bd, i
-	.ifnc		\bd, v10
+	.ifnc		\bd, fold_consts
 	.err
 	.endif
 	mov		ad.16b, \ad\().16b
 	.ifb		\i
-	pmull		\rq\().8h, \ad\().8b, bd.8b		// D = A*B
+	pmull		\rq\().8h, \ad\().8b, \bd\().8b		// D = A*B
 	.else
-	pmull2		\rq\().8h, \ad\().16b, bd.16b		// D = A*B
+	pmull2		\rq\().8h, \ad\().16b, \bd\().16b	// D = A*B
 	.endif
 
 	bl		.L__pmull_p8_core\i
@@ -219,17 +213,19 @@ ENDPROC(__pmull_p8_core)
 	eor		\rq\().16b, \rq\().16b, t6.16b
 	.endm
 
-	.macro		fold64, p, reg1, reg2
-	ldp		q11, q12, [arg2], #0x20
+	// Fold reg1, reg2 into the next 32 data bytes, storing the result back
+	// into reg1, reg2.
+	.macro		fold_32_bytes, p, reg1, reg2
+	ldp		q11, q12, [buf], #0x20
 
-	__pmull_\p	v8, \reg1, v10, 2
-	__pmull_\p	\reg1, \reg1, v10
+	__pmull_\p	v8, \reg1, fold_consts, 2
+	__pmull_\p	\reg1, \reg1, fold_consts
 
 CPU_LE(	rev64		v11.16b, v11.16b		)
 CPU_LE(	rev64		v12.16b, v12.16b		)
 
-	__pmull_\p	v9, \reg2, v10, 2
-	__pmull_\p	\reg2, \reg2, v10
+	__pmull_\p	v9, \reg2, fold_consts, 2
+	__pmull_\p	\reg2, \reg2, fold_consts
 
 CPU_LE(	ext		v11.16b, v11.16b, v11.16b, #8	)
 CPU_LE(	ext		v12.16b, v12.16b, v12.16b, #8	)
@@ -240,15 +236,16 @@ CPU_LE(	ext		v12.16b, v12.16b, v12.16b, #8	)
 	eor		\reg2\().16b, \reg2\().16b, v12.16b
 	.endm
 
-	.macro		fold16, p, reg, rk
-	__pmull_\p	v8, \reg, v10
-	__pmull_\p	\reg, \reg, v10, 2
-	.ifnb		\rk
-	ldr_l		q10, \rk, x8
-	__pmull_pre_\p	v10
+	// Fold src_reg into dst_reg, optionally loading the next fold constants
+	.macro		fold_16_bytes, p, src_reg, dst_reg, load_next_consts
+	__pmull_\p	v8, \src_reg, fold_consts
+	__pmull_\p	\src_reg, \src_reg, fold_consts, 2
+	.ifnb		\load_next_consts
+	ld1		{fold_consts.2d}, [fold_consts_ptr], #16
+	__pmull_pre_\p	fold_consts
 	.endif
-	eor		v7.16b, v7.16b, v8.16b
-	eor		v7.16b, v7.16b, \reg\().16b
+	eor		\dst_reg\().16b, \dst_reg\().16b, v8.16b
+	eor		\dst_reg\().16b, \dst_reg\().16b, \src_reg\().16b
 	.endm
 
 	.macro		__pmull_p64, rd, rn, rm, n
@@ -260,40 +257,27 @@ CPU_LE(	ext		v12.16b, v12.16b, v12.16b, #8	)
 	.endm
 
 	.macro		crc_t10dif_pmull, p
-	frame_push	3, 128
+	frame_push	4, 128
 
-	mov		arg1_low32, w0
-	mov		arg2, x1
-	mov		arg3, x2
-
-	movi		vzr.16b, #0		// init zero register
+	mov		init_crc, w0
+	mov		buf, x1
+	mov		len, x2
 
 	__pmull_init_\p
 
-	// adjust the 16-bit initial_crc value, scale it to 32 bits
-	lsl		arg1_low32, arg1_low32, #16
-
-	// check if smaller than 256
-	cmp		arg3, #256
-
-	// for sizes less than 128, we can't fold 64B at a time...
-	b.lt		.L_less_than_128_\@
+	// For sizes less than 256 bytes, we can't fold 128 bytes at a time.
+	cmp		len, #256
+	b.lt		.Lless_than_256_bytes_\@
 
-	// load the initial crc value
-	// crc value does not need to be byte-reflected, but it needs
-	// to be moved to the high part of the register.
-	// because data will be byte-reflected and will align with
-	// initial crc at correct place.
-	movi		v10.16b, #0
-	mov		v10.s[3], arg1_low32		// initial crc
-
-	// receive the initial 64B data, xor the initial crc value
-	ldp		q0, q1, [arg2]
-	ldp		q2, q3, [arg2, #0x20]
-	ldp		q4, q5, [arg2, #0x40]
-	ldp		q6, q7, [arg2, #0x60]
-	add		arg2, arg2, #0x80
+	adr_l		fold_consts_ptr, .Lfold_across_128_bytes_consts
 
+	// Load the first 128 data bytes.  Byte swapping is necessary to make
+	// the bit order match the polynomial coefficient order.
+	ldp		q0, q1, [buf]
+	ldp		q2, q3, [buf, #0x20]
+	ldp		q4, q5, [buf, #0x40]
+	ldp		q6, q7, [buf, #0x60]
+	add		buf, buf, #0x80
 CPU_LE(	rev64		v0.16b, v0.16b			)
 CPU_LE(	rev64		v1.16b, v1.16b			)
 CPU_LE(	rev64		v2.16b, v2.16b			)
@@ -302,7 +286,6 @@ CPU_LE(	rev64		v4.16b, v4.16b			)
 CPU_LE(	rev64		v5.16b, v5.16b			)
 CPU_LE(	rev64		v6.16b, v6.16b			)
 CPU_LE(	rev64		v7.16b, v7.16b			)
-
 CPU_LE(	ext		v0.16b, v0.16b, v0.16b, #8	)
 CPU_LE(	ext		v1.16b, v1.16b, v1.16b, #8	)
 CPU_LE(	ext		v2.16b, v2.16b, v2.16b, #8	)
@@ -312,36 +295,29 @@ CPU_LE(	ext		v5.16b, v5.16b, v5.16b, #8	)
 CPU_LE(	ext		v6.16b, v6.16b, v6.16b, #8	)
 CPU_LE(	ext		v7.16b, v7.16b, v7.16b, #8	)
 
-	// XOR the initial_crc value
-	eor		v0.16b, v0.16b, v10.16b
-
-	ldr_l		q10, rk3, x8	// xmm10 has rk3 and rk4
-					// type of pmull instruction
-					// will determine which constant to use
-	__pmull_pre_\p	v10
-
-	//
-	// we subtract 256 instead of 128 to save one instruction from the loop
-	//
-	sub		arg3, arg3, #256
-
-	// at this section of the code, there is 64*x+y (0<=y<64) bytes of
-	// buffer. The _fold_64_B_loop will fold 64B at a time
-	// until we have 64+y Bytes of buffer
+	// XOR the first 16 data *bits* with the initial CRC value.
+	movi		v8.16b, #0
+	mov		v8.h[7], init_crc
+	eor		v0.16b, v0.16b, v8.16b
 
-	// fold 64B at a time. This section of the code folds 4 vector
-	// registers in parallel
-.L_fold_64_B_loop_\@:
+	// Load the constants for folding across 128 bytes.
+	ld1		{fold_consts.2d}, [fold_consts_ptr]
+	__pmull_pre_\p	fold_consts
 
-	fold64		\p, v0, v1
-	fold64		\p, v2, v3
-	fold64		\p, v4, v5
-	fold64		\p, v6, v7
+	// Subtract 128 for the 128 data bytes just consumed.  Subtract another
+	// 128 to simplify the termination condition of the following loop.
+	sub		len, len, #256
 
-	subs		arg3, arg3, #128
+	// While >= 128 data bytes remain (not counting v0-v7), fold the 128
+	// bytes v0-v7 into them, storing the result back into v0-v7.
+.Lfold_128_bytes_loop_\@:
+	fold_32_bytes	\p, v0, v1
+	fold_32_bytes	\p, v2, v3
+	fold_32_bytes	\p, v4, v5
+	fold_32_bytes	\p, v6, v7
 
-	// check if there is another 64B in the buffer to be able to fold
-	b.lt		.L_fold_64_B_end_\@
+	subs		len, len, #128
+	b.lt		.Lfold_128_bytes_loop_done_\@
 
 	if_will_cond_yield_neon
 	stp		q0, q1, [sp, #.Lframe_local_offset]
@@ -353,217 +329,207 @@ CPU_LE(	ext		v7.16b, v7.16b, v7.16b, #8	)
 	ldp		q2, q3, [sp, #.Lframe_local_offset + 32]
 	ldp		q4, q5, [sp, #.Lframe_local_offset + 64]
 	ldp		q6, q7, [sp, #.Lframe_local_offset + 96]
-	ldr_l		q10, rk3, x8
-	movi		vzr.16b, #0		// init zero register
+	ld1		{fold_consts.2d}, [fold_consts_ptr]
 	__pmull_init_\p
-	__pmull_pre_\p	v10
+	__pmull_pre_\p	fold_consts
 	endif_yield_neon
 
-	b		.L_fold_64_B_loop_\@
-
-.L_fold_64_B_end_\@:
-	// at this point, the buffer pointer is pointing at the last y Bytes
-	// of the buffer the 64B of folded data is in 4 of the vector
-	// registers: v0, v1, v2, v3
-
-	// fold the 8 vector registers to 1 vector register with different
-	// constants
-
-	ldr_l		q10, rk9, x8
-	__pmull_pre_\p	v10
-
-	fold16		\p, v0, rk11
-	fold16		\p, v1, rk13
-	fold16		\p, v2, rk15
-	fold16		\p, v3, rk17
-	fold16		\p, v4, rk19
-	fold16		\p, v5, rk1
-	fold16		\p, v6
-
-	// instead of 64, we add 48 to the loop counter to save 1 instruction
-	// from the loop instead of a cmp instruction, we use the negative
-	// flag with the jl instruction
-	adds		arg3, arg3, #(128-16)
-	b.lt		.L_final_reduction_for_128_\@
-
-	// now we have 16+y bytes left to reduce. 16 Bytes is in register v7
-	// and the rest is in memory. We can fold 16 bytes at a time if y>=16
-	// continue folding 16B at a time
-
-.L_16B_reduction_loop_\@:
-	__pmull_\p	v8, v7, v10
-	__pmull_\p	v7, v7, v10, 2
+	b		.Lfold_128_bytes_loop_\@
+
+.Lfold_128_bytes_loop_done_\@:
+
+	// Now fold the 112 bytes in v0-v6 into the 16 bytes in v7.
+
+	// Fold across 64 bytes.
+	add		fold_consts_ptr, fold_consts_ptr, #16
+	ld1		{fold_consts.2d}, [fold_consts_ptr], #16
+	__pmull_pre_\p	fold_consts
+	fold_16_bytes	\p, v0, v4
+	fold_16_bytes	\p, v1, v5
+	fold_16_bytes	\p, v2, v6
+	fold_16_bytes	\p, v3, v7, 1
+	// Fold across 32 bytes.
+	fold_16_bytes	\p, v4, v6
+	fold_16_bytes	\p, v5, v7, 1
+	// Fold across 16 bytes.
+	fold_16_bytes	\p, v6, v7
+
+	// Add 128 to get the correct number of data bytes remaining in 0...127
+	// (not counting v7), following the previous extra subtraction by 128.
+	// Then subtract 16 to simplify the termination condition of the
+	// following loop.
+	adds		len, len, #(128-16)
+
+	// While >= 16 data bytes remain (not counting v7), fold the 16 bytes v7
+	// into them, storing the result back into v7.
+	b.lt		.Lfold_16_bytes_loop_done_\@
+.Lfold_16_bytes_loop_\@:
+	__pmull_\p	v8, v7, fold_consts
+	__pmull_\p	v7, v7, fold_consts, 2
 	eor		v7.16b, v7.16b, v8.16b
-
-	ldr		q0, [arg2], #16
+	ldr		q0, [buf], #16
 CPU_LE(	rev64		v0.16b, v0.16b			)
 CPU_LE(	ext		v0.16b, v0.16b, v0.16b, #8	)
 	eor		v7.16b, v7.16b, v0.16b
-	subs		arg3, arg3, #16
-
-	// instead of a cmp instruction, we utilize the flags with the
-	// jge instruction equivalent of: cmp arg3, 16-16
-	// check if there is any more 16B in the buffer to be able to fold
-	b.ge		.L_16B_reduction_loop_\@
-
-	// now we have 16+z bytes left to reduce, where 0<= z < 16.
-	// first, we reduce the data in the xmm7 register
-
-.L_final_reduction_for_128_\@:
-	// check if any more data to fold. If not, compute the CRC of
-	// the final 128 bits
-	adds		arg3, arg3, #16
-	b.eq		.L_128_done_\@
-
-	// here we are getting data that is less than 16 bytes.
-	// since we know that there was data before the pointer, we can
-	// offset the input pointer before the actual point, to receive
-	// exactly 16 bytes. after that the registers need to be adjusted.
-.L_get_last_two_regs_\@:
-	add		arg2, arg2, arg3
-	ldr		q1, [arg2, #-16]
-CPU_LE(	rev64		v1.16b, v1.16b			)
-CPU_LE(	ext		v1.16b, v1.16b, v1.16b, #8	)
-
-	// get rid of the extra data that was loaded before
-	// load the shift constant
-	adr_l		x4, tbl_shf_table + 16
-	sub		x4, x4, arg3
-	ld1		{v0.16b}, [x4]
-
-	// shift v2 to the left by arg3 bytes
-	tbl		v2.16b, {v7.16b}, v0.16b
-
-	// shift v7 to the right by 16-arg3 bytes
-	movi		v9.16b, #0x80
-	eor		v0.16b, v0.16b, v9.16b
-	tbl		v7.16b, {v7.16b}, v0.16b
-
-	// blend
-	sshr		v0.16b, v0.16b, #7	// convert to 8-bit mask
-	bsl		v0.16b, v2.16b, v1.16b
-
-	// fold 16 Bytes
-	__pmull_\p	v8, v7, v10
-	__pmull_\p	v7, v7, v10, 2
-	eor		v7.16b, v7.16b, v8.16b
-	eor		v7.16b, v7.16b, v0.16b
+	subs		len, len, #16
+	b.ge		.Lfold_16_bytes_loop_\@
+
+.Lfold_16_bytes_loop_done_\@:
+	// Add 16 to get the correct number of data bytes remaining in 0...15
+	// (not counting v7), following the previous extra subtraction by 16.
+	adds		len, len, #16
+	b.eq		.Lreduce_final_16_bytes_\@
+
+.Lhandle_partial_segment_\@:
+	// Reduce the last '16 + len' bytes where 1 <= len <= 15 and the first
+	// 16 bytes are in v7 and the rest are the remaining data in 'buf'.  To
+	// do this without needing a fold constant for each possible 'len',
+	// redivide the bytes into a first chunk of 'len' bytes and a second
+	// chunk of 16 bytes, then fold the first chunk into the second.
+
+	// v0 = last 16 original data bytes
+	add		buf, buf, len
+	ldr		q0, [buf, #-16]
+CPU_LE(	rev64		v0.16b, v0.16b			)
+CPU_LE(	ext		v0.16b, v0.16b, v0.16b, #8	)
 
-.L_128_done_\@:
-	// compute crc of a 128-bit value
-	ldr_l		q10, rk5, x8		// rk5 and rk6 in xmm10
-	__pmull_pre_\p	v10
+	// v1 = high order part of second chunk: v7 left-shifted by 'len' bytes.
+	adr_l		x4, .Lbyteshift_table + 16
+	sub		x4, x4, len
+	ld1		{v2.16b}, [x4]
+	tbl		v1.16b, {v7.16b}, v2.16b
 
-	// 64b fold
-	ext		v0.16b, vzr.16b, v7.16b, #8
-	mov		v7.d[0], v7.d[1]
-	__pmull_\p	v7, v7, v10
-	eor		v7.16b, v7.16b, v0.16b
+	// v3 = first chunk: v7 right-shifted by '16-len' bytes.
+	movi		v3.16b, #0x80
+	eor		v2.16b, v2.16b, v3.16b
+	tbl		v3.16b, {v7.16b}, v2.16b
 
-	// 32b fold
-	ext		v0.16b, v7.16b, vzr.16b, #4
-	mov		v7.s[3], vzr.s[0]
-	__pmull_\p	v0, v0, v10, 2
-	eor		v7.16b, v7.16b, v0.16b
+	// Convert to 8-bit masks: 'len' 0x00 bytes, then '16-len' 0xff bytes.
+	sshr		v2.16b, v2.16b, #7
 
-	// barrett reduction
-	ldr_l		q10, rk7, x8
-	__pmull_pre_\p	v10
-	mov		v0.d[0], v7.d[1]
+	// v2 = second chunk: 'len' bytes from v0 (low-order bytes),
+	// then '16-len' bytes from v1 (high-order bytes).
+	bsl		v2.16b, v1.16b, v0.16b
 
-	__pmull_\p	v0, v0, v10
-	ext		v0.16b, vzr.16b, v0.16b, #12
-	__pmull_\p	v0, v0, v10, 2
-	ext		v0.16b, vzr.16b, v0.16b, #12
+	// Fold the first chunk into the second chunk, storing the result in v7.
+	__pmull_\p	v0, v3, fold_consts
+	__pmull_\p	v7, v3, fold_consts, 2
 	eor		v7.16b, v7.16b, v0.16b
-	mov		w0, v7.s[1]
-
-.L_cleanup_\@:
-	// scale the result back to 16 bits
-	lsr		x0, x0, #16
+	eor		v7.16b, v7.16b, v2.16b
+
+.Lreduce_final_16_bytes_\@:
+	// Reduce the 128-bit value M(x), stored in v7, to the final 16-bit CRC.
+
+	movi		v2.16b, #0		// init zero register
+
+	// Load 'x^48 * (x^48 mod G(x))' and 'x^48 * (x^80 mod G(x))'.
+	ld1		{fold_consts.2d}, [fold_consts_ptr], #16
+	__pmull_pre_\p	fold_consts
+
+	// Fold the high 64 bits into the low 64 bits, while also multiplying by
+	// x^64.  This produces a 128-bit value congruent to x^64 * M(x) and
+	// whose low 48 bits are 0.
+	ext		v0.16b, v2.16b, v7.16b, #8
+	__pmull_\p	v7, v7, fold_consts, 2	// high bits * x^48 * (x^80 mod G(x))
+	eor		v0.16b, v0.16b, v7.16b	// + low bits * x^64
+
+	// Fold the high 32 bits into the low 96 bits.  This produces a 96-bit
+	// value congruent to x^64 * M(x) and whose low 48 bits are 0.
+	ext		v1.16b, v0.16b, v2.16b, #12	// extract high 32 bits
+	mov		v0.s[3], v2.s[0]	// zero high 32 bits
+	__pmull_\p	v1, v1, fold_consts	// high 32 bits * x^48 * (x^48 mod G(x))
+	eor		v0.16b, v0.16b, v1.16b	// + low bits
+
+	// Load G(x) and floor(x^48 / G(x)).
+	ld1		{fold_consts.2d}, [fold_consts_ptr]
+	__pmull_pre_\p	fold_consts
+
+	// Use Barrett reduction to compute the final CRC value.
+	__pmull_\p	v1, v0, fold_consts, 2	// high 32 bits * floor(x^48 / G(x))
+	ushr		v1.2d, v1.2d, #32	// /= x^32
+	__pmull_\p	v1, v1, fold_consts	// *= G(x)
+	ushr		v0.2d, v0.2d, #48
+	eor		v0.16b, v0.16b, v1.16b	// + low 16 nonzero bits
+	// Final CRC value (x^16 * M(x)) mod G(x) is in low 16 bits of v0.
+
+	umov		w0, v0.h[0]
 	frame_pop
 	ret
 
-.L_less_than_128_\@:
-	cbz		arg3, .L_cleanup_\@
+.Lless_than_256_bytes_\@:
+	// Checksumming a buffer of length 16...255 bytes
 
-	movi		v0.16b, #0
-	mov		v0.s[3], arg1_low32	// get the initial crc value
+	adr_l		fold_consts_ptr, .Lfold_across_16_bytes_consts
 
-	ldr		q7, [arg2], #0x10
+	// Load the first 16 data bytes.
+	ldr		q7, [buf], #0x10
 CPU_LE(	rev64		v7.16b, v7.16b			)
 CPU_LE(	ext		v7.16b, v7.16b, v7.16b, #8	)
-	eor		v7.16b, v7.16b, v0.16b	// xor the initial crc value
-
-	cmp		arg3, #16
-	b.eq		.L_128_done_\@		// exactly 16 left
 
-	ldr_l		q10, rk1, x8		// rk1 and rk2 in xmm10
-	__pmull_pre_\p	v10
+	// XOR the first 16 data *bits* with the initial CRC value.
+	movi		v0.16b, #0
+	mov		v0.h[7], init_crc
+	eor		v7.16b, v7.16b, v0.16b
 
-	// update the counter. subtract 32 instead of 16 to save one
-	// instruction from the loop
-	subs		arg3, arg3, #32
-	b.ge		.L_16B_reduction_loop_\@
+	// Load the fold-across-16-bytes constants.
+	ld1		{fold_consts.2d}, [fold_consts_ptr], #16
+	__pmull_pre_\p	fold_consts
 
-	add		arg3, arg3, #16
-	b		.L_get_last_two_regs_\@
+	cmp		len, #16
+	b.eq		.Lreduce_final_16_bytes_\@	// len == 16
+	subs		len, len, #32
+	b.ge		.Lfold_16_bytes_loop_\@		// 32 <= len <= 255
+	add		len, len, #16
+	b		.Lhandle_partial_segment_\@	// 17 <= len <= 31
 	.endm
 
+//
+// u16 crc_t10dif_pmull_p8(u16 init_crc, const u8 *buf, size_t len);
+//
+// Assumes len >= 16.
+//
 ENTRY(crc_t10dif_pmull_p8)
 	crc_t10dif_pmull	p8
 ENDPROC(crc_t10dif_pmull_p8)
 
 	.align		5
+//
+// u16 crc_t10dif_pmull_p64(u16 init_crc, const u8 *buf, size_t len);
+//
+// Assumes len >= 16.
+//
 ENTRY(crc_t10dif_pmull_p64)
 	crc_t10dif_pmull	p64
 ENDPROC(crc_t10dif_pmull_p64)
 
-// precomputed constants
-// these constants are precomputed from the poly:
-// 0x8bb70000 (0x8bb7 scaled to 32 bits)
 	.section	".rodata", "a"
 	.align		4
-// Q = 0x18BB70000
-// rk1 = 2^(32*3) mod Q << 32
-// rk2 = 2^(32*5) mod Q << 32
-// rk3 = 2^(32*15) mod Q << 32
-// rk4 = 2^(32*17) mod Q << 32
-// rk5 = 2^(32*3) mod Q << 32
-// rk6 = 2^(32*2) mod Q << 32
-// rk7 = floor(2^64/Q)
-// rk8 = Q
-
-rk1:	.octa		0x06df0000000000002d56000000000000
-rk3:	.octa		0x7cf50000000000009d9d000000000000
-rk5:	.octa		0x13680000000000002d56000000000000
-rk7:	.octa		0x000000018bb7000000000001f65a57f8
-rk9:	.octa		0xbfd6000000000000ceae000000000000
-rk11:	.octa		0x713c0000000000001e16000000000000
-rk13:	.octa		0x80a6000000000000f7f9000000000000
-rk15:	.octa		0xe658000000000000044c000000000000
-rk17:	.octa		0xa497000000000000ad18000000000000
-rk19:	.octa		0xe7b50000000000006ee3000000000000
-
-tbl_shf_table:
-// use these values for shift constants for the tbl/tbx instruction
-// different alignments result in values as shown:
-//	DDQ 0x008f8e8d8c8b8a898887868584838281 # shl 15 (16-1) / shr1
-//	DDQ 0x01008f8e8d8c8b8a8988878685848382 # shl 14 (16-3) / shr2
-//	DDQ 0x0201008f8e8d8c8b8a89888786858483 # shl 13 (16-4) / shr3
-//	DDQ 0x030201008f8e8d8c8b8a898887868584 # shl 12 (16-4) / shr4
-//	DDQ 0x04030201008f8e8d8c8b8a8988878685 # shl 11 (16-5) / shr5
-//	DDQ 0x0504030201008f8e8d8c8b8a89888786 # shl 10 (16-6) / shr6
-//	DDQ 0x060504030201008f8e8d8c8b8a898887 # shl 9  (16-7) / shr7
-//	DDQ 0x07060504030201008f8e8d8c8b8a8988 # shl 8  (16-8) / shr8
-//	DDQ 0x0807060504030201008f8e8d8c8b8a89 # shl 7  (16-9) / shr9
-//	DDQ 0x090807060504030201008f8e8d8c8b8a # shl 6  (16-10) / shr10
-//	DDQ 0x0a090807060504030201008f8e8d8c8b # shl 5  (16-11) / shr11
-//	DDQ 0x0b0a090807060504030201008f8e8d8c # shl 4  (16-12) / shr12
-//	DDQ 0x0c0b0a090807060504030201008f8e8d # shl 3  (16-13) / shr13
-//	DDQ 0x0d0c0b0a090807060504030201008f8e # shl 2  (16-14) / shr14
-//	DDQ 0x0e0d0c0b0a090807060504030201008f # shl 1  (16-15) / shr15
 
+// Fold constants precomputed from the polynomial 0x18bb7
+// G(x) = x^16 + x^15 + x^11 + x^9 + x^8 + x^7 + x^5 + x^4 + x^2 + x^1 + x^0
+.Lfold_across_128_bytes_consts:
+	.quad		0x0000000000006123	// x^(8*128)	mod G(x)
+	.quad		0x0000000000002295	// x^(8*128+64)	mod G(x)
+// .Lfold_across_64_bytes_consts:
+	.quad		0x0000000000001069	// x^(4*128)	mod G(x)
+	.quad		0x000000000000dd31	// x^(4*128+64)	mod G(x)
+// .Lfold_across_32_bytes_consts:
+	.quad		0x000000000000857d	// x^(2*128)	mod G(x)
+	.quad		0x0000000000007acc	// x^(2*128+64)	mod G(x)
+.Lfold_across_16_bytes_consts:
+	.quad		0x000000000000a010	// x^(1*128)	mod G(x)
+	.quad		0x0000000000001faa	// x^(1*128+64)	mod G(x)
+// .Lfinal_fold_consts:
+	.quad		0x1368000000000000	// x^48 * (x^48 mod G(x))
+	.quad		0x2d56000000000000	// x^48 * (x^80 mod G(x))
+// .Lbarrett_reduction_consts:
+	.quad		0x0000000000018bb7	// G(x)
+	.quad		0x00000001f65a57f8	// floor(x^48 / G(x))
+
+// For 1 <= len <= 15, the 16-byte vector beginning at &byteshift_table[16 -
+// len] is the index vector to shift left by 'len' bytes, and is also {0x80,
+// ..., 0x80} XOR the index vector to shift right by '16 - len' bytes.
+.Lbyteshift_table:
 	.byte		 0x0, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87
 	.byte		0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f
 	.byte		 0x0,  0x1,  0x2,  0x3,  0x4,  0x5,  0x6,  0x7
diff --git a/arch/arm64/crypto/crct10dif-ce-glue.c b/arch/arm64/crypto/crct10dif-ce-glue.c
index 242757cc6da91..dd325829ee44f 100644
--- a/arch/arm64/crypto/crct10dif-ce-glue.c
+++ b/arch/arm64/crypto/crct10dif-ce-glue.c
@@ -22,8 +22,8 @@
 
 #define CRC_T10DIF_PMULL_CHUNK_SIZE	16U
 
-asmlinkage u16 crc_t10dif_pmull_p64(u16 init_crc, const u8 buf[], u64 len);
-asmlinkage u16 crc_t10dif_pmull_p8(u16 init_crc, const u8 buf[], u64 len);
+asmlinkage u16 crc_t10dif_pmull_p8(u16 init_crc, const u8 *buf, size_t len);
+asmlinkage u16 crc_t10dif_pmull_p64(u16 init_crc, const u8 *buf, size_t len);
 
 static int crct10dif_init(struct shash_desc *desc)
 {
-- 
2.20.1

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