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Use primitive generator 3 for AES Cauchy mode

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Andrea Mazzoleni 2026-08-19 01:36:18 +02:00
parent f855bf4d82
commit b5d507fbe9
21 changed files with 7444 additions and 5791 deletions
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33
raid/raid.h
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@ -9,23 +9,26 @@
*
* RAID parity computation operates in GF(2^8), a finite field where
* arithmetic is performed modulo an irreducible polynomial of degree 8.
* The choice of polynomial affects both correctness and performance:
* all tables, coefficients, and parity data are tied to a specific
* polynomial and cannot be mixed.
* The choice of operating mode affects both correctness and performance:
* all tables, coefficients, and parity data are tied to the selected
* polynomial and primitive generator and cannot be mixed between
* incompatible operating modes.
*
* Two polynomials are supported:
*
* 0x1d (x^8 + x^4 + x^3 + x^2 + 1) -- Standard RAID polynomial
*
* The polynomial used by the original RAID-6 specification and the
* Linux kernel RAID implementation. Choosing this polynomial ensures
* on-disk compatibility with existing RAID arrays and interchange with
* other RAID implementations. Use this when reading or writing data
* that may be accessed by other software or hardware RAID controllers.
* Linux kernel RAID implementation, used with primitive generator g=2.
* Choosing this polynomial ensures on-disk compatibility with existing
* RAID arrays and interchange with other RAID implementations. Use this
* when reading or writing data that may be accessed by other software or
* hardware RAID controllers.
*
* 0x1b (x^8 + x^4 + x^3 + x + 1) -- AES polynomial
*
* The polynomial used by the AES encryption standard. Choosing this
* The polynomial used by the AES encryption standard (0x11b including
* the x^8 term), used with primitive generator g=3. Choosing this
* polynomial enables the use of the Intel GFNI (Galois Field New
* Instructions) extension, specifically the vgf2p8mulb instruction,
* which performs GF(2^8) multiplication natively in hardware using
@ -36,8 +39,8 @@
* single vgf2p8mulb instruction. On CPUs supporting GFNI (Ice Lake and
* later), this yields a significant throughput improvement. The
* trade-off is that parity data is not compatible with arrays using
* the standard 0x1d polynomial, so this option requires that all
* data be generated and recovered using the same polynomial choice.
* the standard 0x1d polynomial (g=2), so this option requires that all
* data be generated and recovered using the same operating mode.
*/
/**
@ -46,7 +49,7 @@
#define RAID_MODE_GET -1
/**
* Default RAID mode supporting up to 6 parities using the standard polynomial 0x1d.
* Default RAID mode supporting up to 6 parities using standard polynomial 0x1d and generator g=2.
*
* Provides high performance on modern CPUs with SSSE3, AVX2, AVX-512, or NEON support.
* Ensures maximum compatibility with standard Linux RAID arrays.
@ -66,11 +69,11 @@
#define RAID_MODE_VANDERMONDE_RAID 1
/**
* RAID mode supporting up to 6 parities using AES polynomial 0x1b.
* RAID mode supporting up to 6 parities using AES polynomial 0x1b (0x11b) and primitive generator g=3.
*
* It has the same performance as RAID_MODE_CAUCHY_RAID on CPUs without GFNI,
* but achieves significantly higher throughput on CPUs supporting GFNI hardware
* acceleration.
* It has slightly lower performance than RAID_MODE_CAUCHY_RAID on CPUs without GFNI due
* to the additional cost of generator g=3, but achieves significantly higher throughput on
* CPUs supporting GFNI hardware acceleration.
*/
#define RAID_MODE_CAUCHY_AES 2