raid6: Add LoongArch SIMD syndrome calculation

The algorithms work on 64 bytes at a time, which is the L1 cache line
size of all current and future LoongArch cores (that we care about), as
confirmed by Huacai. The code is based on the generic int.uc algorithm,
unrolled 4 times for LSX and 2 times for LASX. Further unrolling does
not meaningfully improve the performance according to experiments.

Performance numbers measured during system boot on a 3A5000 @ 2.5GHz:

> raid6: lasx     gen() 12726 MB/s
> raid6: lsx      gen() 10001 MB/s
> raid6: int64x8  gen()  2876 MB/s
> raid6: int64x4  gen()  3867 MB/s
> raid6: int64x2  gen()  2531 MB/s
> raid6: int64x1  gen()  1945 MB/s

Comparison of xor() speeds (from different boots but meaningful anyway):

> lasx:    11226 MB/s
> lsx:     6395 MB/s
> int64x4: 2147 MB/s

Performance as measured by raid6test:

> raid6: lasx     gen() 25109 MB/s
> raid6: lsx      gen() 13233 MB/s
> raid6: int64x8  gen()  4164 MB/s
> raid6: int64x4  gen()  6005 MB/s
> raid6: int64x2  gen()  5781 MB/s
> raid6: int64x1  gen()  4119 MB/s
> raid6: using algorithm lasx gen() 25109 MB/s
> raid6: .... xor() 14439 MB/s, rmw enabled

Acked-by: Song Liu <song@kernel.org>
Signed-off-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

1 files changed, 422 insertions, 0 deletions

diff --git a/lib/raid6/loongarch_simd.c b/lib/raid6/loongarch_simd.c
new file mode 100644
index 000000000000..aa5d9f924ca3
--- /dev/null
+++ b/lib/raid6/loongarch_simd.c
@@ -0,0 +1,422 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * RAID6 syndrome calculations in LoongArch SIMD (LSX & LASX)
+ *
+ * Copyright 2023 WANG Xuerui <git@xen0n.name>
+ *
+ * Based on the generic RAID-6 code (int.uc):
+ *
+ * Copyright 2002-2004 H. Peter Anvin
+ */
+
+#include <linux/raid/pq.h>
+#include "loongarch.h"
+
+/*
+ * The vector algorithms are currently priority 0, which means the generic
+ * scalar algorithms are not being disabled if vector support is present.
+ * This is like the similar LoongArch RAID5 XOR code, with the main reason
+ * repeated here: it cannot be ruled out at this point of time, that some
+ * future (maybe reduced) models could run the vector algorithms slower than
+ * the scalar ones, maybe for errata or micro-op reasons. It may be
+ * appropriate to revisit this after one or two more uarch generations.
+ */
+
+#ifdef CONFIG_CPU_HAS_LSX
+#define NSIZE 16
+
+static int raid6_has_lsx(void)
+{
+	return cpu_has_lsx;
+}
+
+static void raid6_lsx_gen_syndrome(int disks, size_t bytes, void **ptrs)
+{
+	u8 **dptr = (u8 **)ptrs;
+	u8 *p, *q;
+	int d, z, z0;
+
+	z0 = disks - 3;		/* Highest data disk */
+	p = dptr[z0+1];		/* XOR parity */
+	q = dptr[z0+2];		/* RS syndrome */
+
+	kernel_fpu_begin();
+
+	/*
+	 * $vr0, $vr1, $vr2, $vr3: wp
+	 * $vr4, $vr5, $vr6, $vr7: wq
+	 * $vr8, $vr9, $vr10, $vr11: wd
+	 * $vr12, $vr13, $vr14, $vr15: w2
+	 * $vr16, $vr17, $vr18, $vr19: w1
+	 */
+	for (d = 0; d < bytes; d += NSIZE*4) {
+		/* wq$$ = wp$$ = *(unative_t *)&dptr[z0][d+$$*NSIZE]; */
+		asm volatile("vld $vr0, %0" : : "m"(dptr[z0][d+0*NSIZE]));
+		asm volatile("vld $vr1, %0" : : "m"(dptr[z0][d+1*NSIZE]));
+		asm volatile("vld $vr2, %0" : : "m"(dptr[z0][d+2*NSIZE]));
+		asm volatile("vld $vr3, %0" : : "m"(dptr[z0][d+3*NSIZE]));
+		asm volatile("vori.b $vr4, $vr0, 0");
+		asm volatile("vori.b $vr5, $vr1, 0");
+		asm volatile("vori.b $vr6, $vr2, 0");
+		asm volatile("vori.b $vr7, $vr3, 0");
+		for (z = z0-1; z >= 0; z--) {
+			/* wd$$ = *(unative_t *)&dptr[z][d+$$*NSIZE]; */
+			asm volatile("vld $vr8, %0" : : "m"(dptr[z][d+0*NSIZE]));
+			asm volatile("vld $vr9, %0" : : "m"(dptr[z][d+1*NSIZE]));
+			asm volatile("vld $vr10, %0" : : "m"(dptr[z][d+2*NSIZE]));
+			asm volatile("vld $vr11, %0" : : "m"(dptr[z][d+3*NSIZE]));
+			/* wp$$ ^= wd$$; */
+			asm volatile("vxor.v $vr0, $vr0, $vr8");
+			asm volatile("vxor.v $vr1, $vr1, $vr9");
+			asm volatile("vxor.v $vr2, $vr2, $vr10");
+			asm volatile("vxor.v $vr3, $vr3, $vr11");
+			/* w2$$ = MASK(wq$$); */
+			asm volatile("vslti.b $vr12, $vr4, 0");
+			asm volatile("vslti.b $vr13, $vr5, 0");
+			asm volatile("vslti.b $vr14, $vr6, 0");
+			asm volatile("vslti.b $vr15, $vr7, 0");
+			/* w1$$ = SHLBYTE(wq$$); */
+			asm volatile("vslli.b $vr16, $vr4, 1");
+			asm volatile("vslli.b $vr17, $vr5, 1");
+			asm volatile("vslli.b $vr18, $vr6, 1");
+			asm volatile("vslli.b $vr19, $vr7, 1");
+			/* w2$$ &= NBYTES(0x1d); */
+			asm volatile("vandi.b $vr12, $vr12, 0x1d");
+			asm volatile("vandi.b $vr13, $vr13, 0x1d");
+			asm volatile("vandi.b $vr14, $vr14, 0x1d");
+			asm volatile("vandi.b $vr15, $vr15, 0x1d");
+			/* w1$$ ^= w2$$; */
+			asm volatile("vxor.v $vr16, $vr16, $vr12");
+			asm volatile("vxor.v $vr17, $vr17, $vr13");
+			asm volatile("vxor.v $vr18, $vr18, $vr14");
+			asm volatile("vxor.v $vr19, $vr19, $vr15");
+			/* wq$$ = w1$$ ^ wd$$; */
+			asm volatile("vxor.v $vr4, $vr16, $vr8");
+			asm volatile("vxor.v $vr5, $vr17, $vr9");
+			asm volatile("vxor.v $vr6, $vr18, $vr10");
+			asm volatile("vxor.v $vr7, $vr19, $vr11");
+		}
+		/* *(unative_t *)&p[d+NSIZE*$$] = wp$$; */
+		asm volatile("vst $vr0, %0" : "=m"(p[d+NSIZE*0]));
+		asm volatile("vst $vr1, %0" : "=m"(p[d+NSIZE*1]));
+		asm volatile("vst $vr2, %0" : "=m"(p[d+NSIZE*2]));
+		asm volatile("vst $vr3, %0" : "=m"(p[d+NSIZE*3]));
+		/* *(unative_t *)&q[d+NSIZE*$$] = wq$$; */
+		asm volatile("vst $vr4, %0" : "=m"(q[d+NSIZE*0]));
+		asm volatile("vst $vr5, %0" : "=m"(q[d+NSIZE*1]));
+		asm volatile("vst $vr6, %0" : "=m"(q[d+NSIZE*2]));
+		asm volatile("vst $vr7, %0" : "=m"(q[d+NSIZE*3]));
+	}
+
+	kernel_fpu_end();
+}
+
+static void raid6_lsx_xor_syndrome(int disks, int start, int stop,
+				   size_t bytes, void **ptrs)
+{
+	u8 **dptr = (u8 **)ptrs;
+	u8 *p, *q;
+	int d, z, z0;
+
+	z0 = stop;		/* P/Q right side optimization */
+	p = dptr[disks-2];	/* XOR parity */
+	q = dptr[disks-1];	/* RS syndrome */
+
+	kernel_fpu_begin();
+
+	/*
+	 * $vr0, $vr1, $vr2, $vr3: wp
+	 * $vr4, $vr5, $vr6, $vr7: wq
+	 * $vr8, $vr9, $vr10, $vr11: wd
+	 * $vr12, $vr13, $vr14, $vr15: w2
+	 * $vr16, $vr17, $vr18, $vr19: w1
+	 */
+	for (d = 0; d < bytes; d += NSIZE*4) {
+		/* P/Q data pages */
+		/* wq$$ = wp$$ = *(unative_t *)&dptr[z0][d+$$*NSIZE]; */
+		asm volatile("vld $vr0, %0" : : "m"(dptr[z0][d+0*NSIZE]));
+		asm volatile("vld $vr1, %0" : : "m"(dptr[z0][d+1*NSIZE]));
+		asm volatile("vld $vr2, %0" : : "m"(dptr[z0][d+2*NSIZE]));
+		asm volatile("vld $vr3, %0" : : "m"(dptr[z0][d+3*NSIZE]));
+		asm volatile("vori.b $vr4, $vr0, 0");
+		asm volatile("vori.b $vr5, $vr1, 0");
+		asm volatile("vori.b $vr6, $vr2, 0");
+		asm volatile("vori.b $vr7, $vr3, 0");
+		for (z = z0-1; z >= start; z--) {
+			/* wd$$ = *(unative_t *)&dptr[z][d+$$*NSIZE]; */
+			asm volatile("vld $vr8, %0" : : "m"(dptr[z][d+0*NSIZE]));
+			asm volatile("vld $vr9, %0" : : "m"(dptr[z][d+1*NSIZE]));
+			asm volatile("vld $vr10, %0" : : "m"(dptr[z][d+2*NSIZE]));
+			asm volatile("vld $vr11, %0" : : "m"(dptr[z][d+3*NSIZE]));
+			/* wp$$ ^= wd$$; */
+			asm volatile("vxor.v $vr0, $vr0, $vr8");
+			asm volatile("vxor.v $vr1, $vr1, $vr9");
+			asm volatile("vxor.v $vr2, $vr2, $vr10");
+			asm volatile("vxor.v $vr3, $vr3, $vr11");
+			/* w2$$ = MASK(wq$$); */
+			asm volatile("vslti.b $vr12, $vr4, 0");
+			asm volatile("vslti.b $vr13, $vr5, 0");
+			asm volatile("vslti.b $vr14, $vr6, 0");
+			asm volatile("vslti.b $vr15, $vr7, 0");
+			/* w1$$ = SHLBYTE(wq$$); */
+			asm volatile("vslli.b $vr16, $vr4, 1");
+			asm volatile("vslli.b $vr17, $vr5, 1");
+			asm volatile("vslli.b $vr18, $vr6, 1");
+			asm volatile("vslli.b $vr19, $vr7, 1");
+			/* w2$$ &= NBYTES(0x1d); */
+			asm volatile("vandi.b $vr12, $vr12, 0x1d");
+			asm volatile("vandi.b $vr13, $vr13, 0x1d");
+			asm volatile("vandi.b $vr14, $vr14, 0x1d");
+			asm volatile("vandi.b $vr15, $vr15, 0x1d");
+			/* w1$$ ^= w2$$; */
+			asm volatile("vxor.v $vr16, $vr16, $vr12");
+			asm volatile("vxor.v $vr17, $vr17, $vr13");
+			asm volatile("vxor.v $vr18, $vr18, $vr14");
+			asm volatile("vxor.v $vr19, $vr19, $vr15");
+			/* wq$$ = w1$$ ^ wd$$; */
+			asm volatile("vxor.v $vr4, $vr16, $vr8");
+			asm volatile("vxor.v $vr5, $vr17, $vr9");
+			asm volatile("vxor.v $vr6, $vr18, $vr10");
+			asm volatile("vxor.v $vr7, $vr19, $vr11");
+		}
+
+		/* P/Q left side optimization */
+		for (z = start-1; z >= 0; z--) {
+			/* w2$$ = MASK(wq$$); */
+			asm volatile("vslti.b $vr12, $vr4, 0");
+			asm volatile("vslti.b $vr13, $vr5, 0");
+			asm volatile("vslti.b $vr14, $vr6, 0");
+			asm volatile("vslti.b $vr15, $vr7, 0");
+			/* w1$$ = SHLBYTE(wq$$); */
+			asm volatile("vslli.b $vr16, $vr4, 1");
+			asm volatile("vslli.b $vr17, $vr5, 1");
+			asm volatile("vslli.b $vr18, $vr6, 1");
+			asm volatile("vslli.b $vr19, $vr7, 1");
+			/* w2$$ &= NBYTES(0x1d); */
+			asm volatile("vandi.b $vr12, $vr12, 0x1d");
+			asm volatile("vandi.b $vr13, $vr13, 0x1d");
+			asm volatile("vandi.b $vr14, $vr14, 0x1d");
+			asm volatile("vandi.b $vr15, $vr15, 0x1d");
+			/* wq$$ = w1$$ ^ w2$$; */
+			asm volatile("vxor.v $vr4, $vr16, $vr12");
+			asm volatile("vxor.v $vr5, $vr17, $vr13");
+			asm volatile("vxor.v $vr6, $vr18, $vr14");
+			asm volatile("vxor.v $vr7, $vr19, $vr15");
+		}
+		/*
+		 * *(unative_t *)&p[d+NSIZE*$$] ^= wp$$;
+		 * *(unative_t *)&q[d+NSIZE*$$] ^= wq$$;
+		 */
+		asm volatile(
+			"vld $vr20, %0\n\t"
+			"vld $vr21, %1\n\t"
+			"vld $vr22, %2\n\t"
+			"vld $vr23, %3\n\t"
+			"vld $vr24, %4\n\t"
+			"vld $vr25, %5\n\t"
+			"vld $vr26, %6\n\t"
+			"vld $vr27, %7\n\t"
+			"vxor.v $vr20, $vr20, $vr0\n\t"
+			"vxor.v $vr21, $vr21, $vr1\n\t"
+			"vxor.v $vr22, $vr22, $vr2\n\t"
+			"vxor.v $vr23, $vr23, $vr3\n\t"
+			"vxor.v $vr24, $vr24, $vr4\n\t"
+			"vxor.v $vr25, $vr25, $vr5\n\t"
+			"vxor.v $vr26, $vr26, $vr6\n\t"
+			"vxor.v $vr27, $vr27, $vr7\n\t"
+			"vst $vr20, %0\n\t"
+			"vst $vr21, %1\n\t"
+			"vst $vr22, %2\n\t"
+			"vst $vr23, %3\n\t"
+			"vst $vr24, %4\n\t"
+			"vst $vr25, %5\n\t"
+			"vst $vr26, %6\n\t"
+			"vst $vr27, %7\n\t"
+			: "+m"(p[d+NSIZE*0]), "+m"(p[d+NSIZE*1]),
+			  "+m"(p[d+NSIZE*2]), "+m"(p[d+NSIZE*3]),
+			  "+m"(q[d+NSIZE*0]), "+m"(q[d+NSIZE*1]),
+			  "+m"(q[d+NSIZE*2]), "+m"(q[d+NSIZE*3])
+		);
+	}
+
+	kernel_fpu_end();
+}
+
+const struct raid6_calls raid6_lsx = {
+	raid6_lsx_gen_syndrome,
+	raid6_lsx_xor_syndrome,
+	raid6_has_lsx,
+	"lsx",
+	.priority = 0 /* see the comment near the top of the file for reason */
+};
+
+#undef NSIZE
+#endif /* CONFIG_CPU_HAS_LSX */
+
+#ifdef CONFIG_CPU_HAS_LASX
+#define NSIZE 32
+
+static int raid6_has_lasx(void)
+{
+	return cpu_has_lasx;
+}
+
+static void raid6_lasx_gen_syndrome(int disks, size_t bytes, void **ptrs)
+{
+	u8 **dptr = (u8 **)ptrs;
+	u8 *p, *q;
+	int d, z, z0;
+
+	z0 = disks - 3;		/* Highest data disk */
+	p = dptr[z0+1];		/* XOR parity */
+	q = dptr[z0+2];		/* RS syndrome */
+
+	kernel_fpu_begin();
+
+	/*
+	 * $xr0, $xr1: wp
+	 * $xr2, $xr3: wq
+	 * $xr4, $xr5: wd
+	 * $xr6, $xr7: w2
+	 * $xr8, $xr9: w1
+	 */
+	for (d = 0; d < bytes; d += NSIZE*2) {
+		/* wq$$ = wp$$ = *(unative_t *)&dptr[z0][d+$$*NSIZE]; */
+		asm volatile("xvld $xr0, %0" : : "m"(dptr[z0][d+0*NSIZE]));
+		asm volatile("xvld $xr1, %0" : : "m"(dptr[z0][d+1*NSIZE]));
+		asm volatile("xvori.b $xr2, $xr0, 0");
+		asm volatile("xvori.b $xr3, $xr1, 0");
+		for (z = z0-1; z >= 0; z--) {
+			/* wd$$ = *(unative_t *)&dptr[z][d+$$*NSIZE]; */
+			asm volatile("xvld $xr4, %0" : : "m"(dptr[z][d+0*NSIZE]));
+			asm volatile("xvld $xr5, %0" : : "m"(dptr[z][d+1*NSIZE]));
+			/* wp$$ ^= wd$$; */
+			asm volatile("xvxor.v $xr0, $xr0, $xr4");
+			asm volatile("xvxor.v $xr1, $xr1, $xr5");
+			/* w2$$ = MASK(wq$$); */
+			asm volatile("xvslti.b $xr6, $xr2, 0");
+			asm volatile("xvslti.b $xr7, $xr3, 0");
+			/* w1$$ = SHLBYTE(wq$$); */
+			asm volatile("xvslli.b $xr8, $xr2, 1");
+			asm volatile("xvslli.b $xr9, $xr3, 1");
+			/* w2$$ &= NBYTES(0x1d); */
+			asm volatile("xvandi.b $xr6, $xr6, 0x1d");
+			asm volatile("xvandi.b $xr7, $xr7, 0x1d");
+			/* w1$$ ^= w2$$; */
+			asm volatile("xvxor.v $xr8, $xr8, $xr6");
+			asm volatile("xvxor.v $xr9, $xr9, $xr7");
+			/* wq$$ = w1$$ ^ wd$$; */
+			asm volatile("xvxor.v $xr2, $xr8, $xr4");
+			asm volatile("xvxor.v $xr3, $xr9, $xr5");
+		}
+		/* *(unative_t *)&p[d+NSIZE*$$] = wp$$; */
+		asm volatile("xvst $xr0, %0" : "=m"(p[d+NSIZE*0]));
+		asm volatile("xvst $xr1, %0" : "=m"(p[d+NSIZE*1]));
+		/* *(unative_t *)&q[d+NSIZE*$$] = wq$$; */
+		asm volatile("xvst $xr2, %0" : "=m"(q[d+NSIZE*0]));
+		asm volatile("xvst $xr3, %0" : "=m"(q[d+NSIZE*1]));
+	}
+
+	kernel_fpu_end();
+}
+
+static void raid6_lasx_xor_syndrome(int disks, int start, int stop,
+				    size_t bytes, void **ptrs)
+{
+	u8 **dptr = (u8 **)ptrs;
+	u8 *p, *q;
+	int d, z, z0;
+
+	z0 = stop;		/* P/Q right side optimization */
+	p = dptr[disks-2];	/* XOR parity */
+	q = dptr[disks-1];	/* RS syndrome */
+
+	kernel_fpu_begin();
+
+	/*
+	 * $xr0, $xr1: wp
+	 * $xr2, $xr3: wq
+	 * $xr4, $xr5: wd
+	 * $xr6, $xr7: w2
+	 * $xr8, $xr9: w1
+	 */
+	for (d = 0; d < bytes; d += NSIZE*2) {
+		/* P/Q data pages */
+		/* wq$$ = wp$$ = *(unative_t *)&dptr[z0][d+$$*NSIZE]; */
+		asm volatile("xvld $xr0, %0" : : "m"(dptr[z0][d+0*NSIZE]));
+		asm volatile("xvld $xr1, %0" : : "m"(dptr[z0][d+1*NSIZE]));
+		asm volatile("xvori.b $xr2, $xr0, 0");
+		asm volatile("xvori.b $xr3, $xr1, 0");
+		for (z = z0-1; z >= start; z--) {
+			/* wd$$ = *(unative_t *)&dptr[z][d+$$*NSIZE]; */
+			asm volatile("xvld $xr4, %0" : : "m"(dptr[z][d+0*NSIZE]));
+			asm volatile("xvld $xr5, %0" : : "m"(dptr[z][d+1*NSIZE]));
+			/* wp$$ ^= wd$$; */
+			asm volatile("xvxor.v $xr0, $xr0, $xr4");
+			asm volatile("xvxor.v $xr1, $xr1, $xr5");
+			/* w2$$ = MASK(wq$$); */
+			asm volatile("xvslti.b $xr6, $xr2, 0");
+			asm volatile("xvslti.b $xr7, $xr3, 0");
+			/* w1$$ = SHLBYTE(wq$$); */
+			asm volatile("xvslli.b $xr8, $xr2, 1");
+			asm volatile("xvslli.b $xr9, $xr3, 1");
+			/* w2$$ &= NBYTES(0x1d); */
+			asm volatile("xvandi.b $xr6, $xr6, 0x1d");
+			asm volatile("xvandi.b $xr7, $xr7, 0x1d");
+			/* w1$$ ^= w2$$; */
+			asm volatile("xvxor.v $xr8, $xr8, $xr6");
+			asm volatile("xvxor.v $xr9, $xr9, $xr7");
+			/* wq$$ = w1$$ ^ wd$$; */
+			asm volatile("xvxor.v $xr2, $xr8, $xr4");
+			asm volatile("xvxor.v $xr3, $xr9, $xr5");
+		}
+
+		/* P/Q left side optimization */
+		for (z = start-1; z >= 0; z--) {
+			/* w2$$ = MASK(wq$$); */
+			asm volatile("xvslti.b $xr6, $xr2, 0");
+			asm volatile("xvslti.b $xr7, $xr3, 0");
+			/* w1$$ = SHLBYTE(wq$$); */
+			asm volatile("xvslli.b $xr8, $xr2, 1");
+			asm volatile("xvslli.b $xr9, $xr3, 1");
+			/* w2$$ &= NBYTES(0x1d); */
+			asm volatile("xvandi.b $xr6, $xr6, 0x1d");
+			asm volatile("xvandi.b $xr7, $xr7, 0x1d");
+			/* wq$$ = w1$$ ^ w2$$; */
+			asm volatile("xvxor.v $xr2, $xr8, $xr6");
+			asm volatile("xvxor.v $xr3, $xr9, $xr7");
+		}
+		/*
+		 * *(unative_t *)&p[d+NSIZE*$$] ^= wp$$;
+		 * *(unative_t *)&q[d+NSIZE*$$] ^= wq$$;
+		 */
+		asm volatile(
+			"xvld $xr10, %0\n\t"
+			"xvld $xr11, %1\n\t"
+			"xvld $xr12, %2\n\t"
+			"xvld $xr13, %3\n\t"
+			"xvxor.v $xr10, $xr10, $xr0\n\t"
+			"xvxor.v $xr11, $xr11, $xr1\n\t"
+			"xvxor.v $xr12, $xr12, $xr2\n\t"
+			"xvxor.v $xr13, $xr13, $xr3\n\t"
+			"xvst $xr10, %0\n\t"
+			"xvst $xr11, %1\n\t"
+			"xvst $xr12, %2\n\t"
+			"xvst $xr13, %3\n\t"
+			: "+m"(p[d+NSIZE*0]), "+m"(p[d+NSIZE*1]),
+			  "+m"(q[d+NSIZE*0]), "+m"(q[d+NSIZE*1])
+		);
+	}
+
+	kernel_fpu_end();
+}
+
+const struct raid6_calls raid6_lasx = {
+	raid6_lasx_gen_syndrome,
+	raid6_lasx_xor_syndrome,
+	raid6_has_lasx,
+	"lasx",
+	.priority = 0 /* see the comment near the top of the file for reason */
+};
+#undef NSIZE
+#endif /* CONFIG_CPU_HAS_LASX */