lib/raid6: Use strict priority ranking for pq gen() benchmarking

On x86_64, currently 3 variants of AVX512, 3 variants of AVX2
and 3 variants of SSE2 are benchmarked on initialization, taking
between 144-153 jiffies. Testing across a hardware pool of
various generations of intel cpus I could not find a single
case where SSE2 won over AVX2 or AVX512. There are cases where
AVX2 wins over AVX512 however.

Change "prefer" into an integer priority field (similar to
how recov selection works) to have more than one ranking level
available, which is backwards compatible with existing behavior.

Give AVX2/512 variants higher priority over SSE2 in order to skip
SSE testing when AVX is available. in a AVX2/x86_64/HZ=250 case this
saves in the order of 200ms of initialization time.

Signed-off-by: Dirk Müller <dmueller@suse.de>
Acked-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Song Liu <song@kernel.org>

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 48

Based on 1 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation inc 53 temple place ste 330 boston ma
02111 1307 usa either version 2 of the license or at your option any
later version incorporated herein by reference

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 13 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190520170858.645641371@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

lib/raid6: align AVX512 constants to 512 bits, not bytes

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: mingo@redhat.com
Cc: Jim Kukunas <james.t.kukunas@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Megha Dey <megha.dey@linux.intel.com>
Cc: Gayatri Kammela <gayatri.kammela@intel.com>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Shaohua Li <shli@fb.com>

lib/raid6: Add AVX512 optimized xor_syndrome functions

Optimize RAID6 xor_syndrome functions to take advantage of the 512-bit
ZMM integer instructions introduced in AVX512.

AVX512 optimized xor_syndrome functions, which is simply based on sse2.c
written by hpa.

The patch was tested and benchmarked before submission on
a hardware that has AVX512 flags to support such instructions

Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jim Kukunas <james.t.kukunas@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Megha Dey <megha.dey@linux.intel.com>
Signed-off-by: Gayatri Kammela <gayatri.kammela@intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>

lib/raid6: Add AVX512 optimized gen_syndrome functions

Optimize RAID6 gen_syndrom functions to take advantage of
the 512-bit ZMM integer instructions introduced in AVX512.

AVX512 optimized gen_syndrom functions, which is simply based
on avx2.c written by Yuanhan Liu and sse2.c written by hpa.

The patch was tested and benchmarked before submission on
a hardware that has AVX512 flags to support such instructions

Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jim Kukunas <james.t.kukunas@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Megha Dey <megha.dey@linux.intel.com>
Signed-off-by: Gayatri Kammela <gayatri.kammela@intel.com>
Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>