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Diffstat (limited to 'lib/crc/s390/crc32be-vx.c')
| -rw-r--r-- | lib/crc/s390/crc32be-vx.c | 174 |
1 files changed, 174 insertions, 0 deletions
diff --git a/lib/crc/s390/crc32be-vx.c b/lib/crc/s390/crc32be-vx.c new file mode 100644 index 000000000000..fed7c9c70d05 --- /dev/null +++ b/lib/crc/s390/crc32be-vx.c @@ -0,0 +1,174 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Hardware-accelerated CRC-32 variants for Linux on z Systems + * + * Use the z/Architecture Vector Extension Facility to accelerate the + * computing of CRC-32 checksums. + * + * This CRC-32 implementation algorithm processes the most-significant + * bit first (BE). + * + * Copyright IBM Corp. 2015 + * Author(s): Hendrik Brueckner <brueckner@linux.vnet.ibm.com> + */ + +#include <linux/types.h> +#include <asm/fpu.h> +#include "crc32-vx.h" + +/* Vector register range containing CRC-32 constants */ +#define CONST_R1R2 9 +#define CONST_R3R4 10 +#define CONST_R5 11 +#define CONST_R6 12 +#define CONST_RU_POLY 13 +#define CONST_CRC_POLY 14 + +/* + * The CRC-32 constant block contains reduction constants to fold and + * process particular chunks of the input data stream in parallel. + * + * For the CRC-32 variants, the constants are precomputed according to + * these definitions: + * + * R1 = x4*128+64 mod P(x) + * R2 = x4*128 mod P(x) + * R3 = x128+64 mod P(x) + * R4 = x128 mod P(x) + * R5 = x96 mod P(x) + * R6 = x64 mod P(x) + * + * Barret reduction constant, u, is defined as floor(x**64 / P(x)). + * + * where P(x) is the polynomial in the normal domain and the P'(x) is the + * polynomial in the reversed (bitreflected) domain. + * + * Note that the constant definitions below are extended in order to compute + * intermediate results with a single VECTOR GALOIS FIELD MULTIPLY instruction. + * The rightmost doubleword can be 0 to prevent contribution to the result or + * can be multiplied by 1 to perform an XOR without the need for a separate + * VECTOR EXCLUSIVE OR instruction. + * + * CRC-32 (IEEE 802.3 Ethernet, ...) polynomials: + * + * P(x) = 0x04C11DB7 + * P'(x) = 0xEDB88320 + */ + +static unsigned long constants_CRC_32_BE[] = { + 0x08833794c, 0x0e6228b11, /* R1, R2 */ + 0x0c5b9cd4c, 0x0e8a45605, /* R3, R4 */ + 0x0f200aa66, 1UL << 32, /* R5, x32 */ + 0x0490d678d, 1, /* R6, 1 */ + 0x104d101df, 0, /* u */ + 0x104C11DB7, 0, /* P(x) */ +}; + +/** + * crc32_be_vgfm_16 - Compute CRC-32 (BE variant) with vector registers + * @crc: Initial CRC value, typically ~0. + * @buf: Input buffer pointer, performance might be improved if the + * buffer is on a doubleword boundary. + * @size: Size of the buffer, must be 64 bytes or greater. + * + * Register usage: + * V0: Initial CRC value and intermediate constants and results. + * V1..V4: Data for CRC computation. + * V5..V8: Next data chunks that are fetched from the input buffer. + * V9..V14: CRC-32 constants. + */ +u32 crc32_be_vgfm_16(u32 crc, unsigned char const *buf, size_t size) +{ + /* Load CRC-32 constants */ + fpu_vlm(CONST_R1R2, CONST_CRC_POLY, &constants_CRC_32_BE); + fpu_vzero(0); + + /* Load the initial CRC value into the leftmost word of V0. */ + fpu_vlvgf(0, crc, 0); + + /* Load a 64-byte data chunk and XOR with CRC */ + fpu_vlm(1, 4, buf); + fpu_vx(1, 0, 1); + buf += 64; + size -= 64; + + while (size >= 64) { + /* Load the next 64-byte data chunk into V5 to V8 */ + fpu_vlm(5, 8, buf); + + /* + * Perform a GF(2) multiplication of the doublewords in V1 with + * the reduction constants in V0. The intermediate result is + * then folded (accumulated) with the next data chunk in V5 and + * stored in V1. Repeat this step for the register contents + * in V2, V3, and V4 respectively. + */ + fpu_vgfmag(1, CONST_R1R2, 1, 5); + fpu_vgfmag(2, CONST_R1R2, 2, 6); + fpu_vgfmag(3, CONST_R1R2, 3, 7); + fpu_vgfmag(4, CONST_R1R2, 4, 8); + buf += 64; + size -= 64; + } + + /* Fold V1 to V4 into a single 128-bit value in V1 */ + fpu_vgfmag(1, CONST_R3R4, 1, 2); + fpu_vgfmag(1, CONST_R3R4, 1, 3); + fpu_vgfmag(1, CONST_R3R4, 1, 4); + + while (size >= 16) { + fpu_vl(2, buf); + fpu_vgfmag(1, CONST_R3R4, 1, 2); + buf += 16; + size -= 16; + } + + /* + * The R5 constant is used to fold a 128-bit value into an 96-bit value + * that is XORed with the next 96-bit input data chunk. To use a single + * VGFMG instruction, multiply the rightmost 64-bit with x^32 (1<<32) to + * form an intermediate 96-bit value (with appended zeros) which is then + * XORed with the intermediate reduction result. + */ + fpu_vgfmg(1, CONST_R5, 1); + + /* + * Further reduce the remaining 96-bit value to a 64-bit value using a + * single VGFMG, the rightmost doubleword is multiplied with 0x1. The + * intermediate result is then XORed with the product of the leftmost + * doubleword with R6. The result is a 64-bit value and is subject to + * the Barret reduction. + */ + fpu_vgfmg(1, CONST_R6, 1); + + /* + * The input values to the Barret reduction are the degree-63 polynomial + * in V1 (R(x)), degree-32 generator polynomial, and the reduction + * constant u. The Barret reduction result is the CRC value of R(x) mod + * P(x). + * + * The Barret reduction algorithm is defined as: + * + * 1. T1(x) = floor( R(x) / x^32 ) GF2MUL u + * 2. T2(x) = floor( T1(x) / x^32 ) GF2MUL P(x) + * 3. C(x) = R(x) XOR T2(x) mod x^32 + * + * Note: To compensate the division by x^32, use the vector unpack + * instruction to move the leftmost word into the leftmost doubleword + * of the vector register. The rightmost doubleword is multiplied + * with zero to not contribute to the intermediate results. + */ + + /* T1(x) = floor( R(x) / x^32 ) GF2MUL u */ + fpu_vupllf(2, 1); + fpu_vgfmg(2, CONST_RU_POLY, 2); + + /* + * Compute the GF(2) product of the CRC polynomial in VO with T1(x) in + * V2 and XOR the intermediate result, T2(x), with the value in V1. + * The final result is in the rightmost word of V2. + */ + fpu_vupllf(2, 2); + fpu_vgfmag(2, CONST_CRC_POLY, 2, 1); + return fpu_vlgvf(2, 3); +} |