LoongArch: Add SIMD-optimized XOR routines

Add LSX and LASX implementations of xor operations, operating on 64
bytes (one L1 cache line) at a time, for a balance between memory
utilization and instruction mix. Huacai confirmed that all future
LoongArch implementations by Loongson (that we care) will likely also
feature 64-byte cache lines, and experiments show no throughput
improvement with further unrolling.

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

> 8regs           : 12702 MB/sec
> 8regs_prefetch  : 10920 MB/sec
> 32regs          : 12686 MB/sec
> 32regs_prefetch : 10918 MB/sec
> lsx             : 17589 MB/sec
> lasx            : 26116 MB/sec
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: WANG Xuerui <git@xen0n.name>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/include/asm/xor.h

+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2023 WANG Xuerui <git@xen0n.name>
+ */
+#ifndef _ASM_LOONGARCH_XOR_H
+#define _ASM_LOONGARCH_XOR_H
+
+#include <asm/cpu-features.h>
+#include <asm/xor_simd.h>
+
+#ifdef CONFIG_CPU_HAS_LSX
+static struct xor_block_template xor_block_lsx = {
+	.name = "lsx",
+	.do_2 = xor_lsx_2,
+	.do_3 = xor_lsx_3,
+	.do_4 = xor_lsx_4,
+	.do_5 = xor_lsx_5,
+};
+
+#define XOR_SPEED_LSX()					\
+	do {						\
+		if (cpu_has_lsx)			\
+			xor_speed(&xor_block_lsx);	\
+	} while (0)
+#else /* CONFIG_CPU_HAS_LSX */
+#define XOR_SPEED_LSX()
+#endif /* CONFIG_CPU_HAS_LSX */
+
+#ifdef CONFIG_CPU_HAS_LASX
+static struct xor_block_template xor_block_lasx = {
+	.name = "lasx",
+	.do_2 = xor_lasx_2,
+	.do_3 = xor_lasx_3,
+	.do_4 = xor_lasx_4,
+	.do_5 = xor_lasx_5,
+};
+
+#define XOR_SPEED_LASX()					\
+	do {							\
+		if (cpu_has_lasx)				\
+			xor_speed(&xor_block_lasx);		\
+	} while (0)
+#else /* CONFIG_CPU_HAS_LASX */
+#define XOR_SPEED_LASX()
+#endif /* CONFIG_CPU_HAS_LASX */
+
+/*
+ * For grins, also test the generic routines.
+ *
+ * More importantly: 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.
+ */
+#include <asm-generic/xor.h>
+
+#undef XOR_TRY_TEMPLATES
+#define XOR_TRY_TEMPLATES				\
+do {							\
+	xor_speed(&xor_block_8regs);			\
+	xor_speed(&xor_block_8regs_p);			\
+	xor_speed(&xor_block_32regs);			\
+	xor_speed(&xor_block_32regs_p);			\
+	XOR_SPEED_LSX();				\
+	XOR_SPEED_LASX();				\
+} while (0)
+
+#endif /* _ASM_LOONGARCH_XOR_H */

arch/loongarch/include/asm/xor_simd.h

+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2023 WANG Xuerui <git@xen0n.name>
+ */
+#ifndef _ASM_LOONGARCH_XOR_SIMD_H
+#define _ASM_LOONGARCH_XOR_SIMD_H
+
+#ifdef CONFIG_CPU_HAS_LSX
+void xor_lsx_2(unsigned long bytes, unsigned long * __restrict p1,
+	       const unsigned long * __restrict p2);
+void xor_lsx_3(unsigned long bytes, unsigned long * __restrict p1,
+	       const unsigned long * __restrict p2, const unsigned long * __restrict p3);
+void xor_lsx_4(unsigned long bytes, unsigned long * __restrict p1,
+	       const unsigned long * __restrict p2, const unsigned long * __restrict p3,
+	       const unsigned long * __restrict p4);
+void xor_lsx_5(unsigned long bytes, unsigned long * __restrict p1,
+	       const unsigned long * __restrict p2, const unsigned long * __restrict p3,
+	       const unsigned long * __restrict p4, const unsigned long * __restrict p5);
+#endif /* CONFIG_CPU_HAS_LSX */
+
+#ifdef CONFIG_CPU_HAS_LASX
+void xor_lasx_2(unsigned long bytes, unsigned long * __restrict p1,
+	        const unsigned long * __restrict p2);
+void xor_lasx_3(unsigned long bytes, unsigned long * __restrict p1,
+	        const unsigned long * __restrict p2, const unsigned long * __restrict p3);
+void xor_lasx_4(unsigned long bytes, unsigned long * __restrict p1,
+	        const unsigned long * __restrict p2, const unsigned long * __restrict p3,
+	        const unsigned long * __restrict p4);
+void xor_lasx_5(unsigned long bytes, unsigned long * __restrict p1,
+	        const unsigned long * __restrict p2, const unsigned long * __restrict p3,
+	        const unsigned long * __restrict p4, const unsigned long * __restrict p5);
+#endif /* CONFIG_CPU_HAS_LASX */
+
+#endif /* _ASM_LOONGARCH_XOR_SIMD_H */

arch/loongarch/lib/Makefile

@@ -6,4 +6,6 @@
 lib-y	+= delay.o memset.o memcpy.o memmove.o \
 	   clear_user.o copy_user.o csum.o dump_tlb.o unaligned.o
 
+obj-$(CONFIG_CPU_HAS_LSX) += xor_simd.o xor_simd_glue.o
+
 obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o

arch/loongarch/lib/xor_simd.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * LoongArch SIMD XOR operations
+ *
+ * Copyright (C) 2023 WANG Xuerui <git@xen0n.name>
+ */
+
+#include "xor_simd.h"
+
+/*
+ * Process one cache line (64 bytes) per loop. This is assuming all future
+ * popular LoongArch cores are similar performance-characteristics-wise to the
+ * current models.
+ */
+#define LINE_WIDTH 64
+
+#ifdef CONFIG_CPU_HAS_LSX
+
+#define LD(reg, base, offset)	\
+	"vld $vr" #reg ", %[" #base "], " #offset "\n\t"
+#define ST(reg, base, offset)	\
+	"vst $vr" #reg ", %[" #base "], " #offset "\n\t"
+#define XOR(dj, k)	"vxor.v $vr" #dj ", $vr" #dj ", $vr" #k "\n\t"
+
+#define LD_INOUT_LINE(base)	\
+	LD(0, base, 0)		\
+	LD(1, base, 16)		\
+	LD(2, base, 32)		\
+	LD(3, base, 48)
+
+#define LD_AND_XOR_LINE(base)	\
+	LD(4, base, 0)		\
+	LD(5, base, 16)		\
+	LD(6, base, 32)		\
+	LD(7, base, 48)		\
+	XOR(0, 4)		\
+	XOR(1, 5)		\
+	XOR(2, 6)		\
+	XOR(3, 7)
+
+#define ST_LINE(base)		\
+	ST(0, base, 0)		\
+	ST(1, base, 16)		\
+	ST(2, base, 32)		\
+	ST(3, base, 48)
+
+#define XOR_FUNC_NAME(nr) __xor_lsx_##nr
+#include "xor_template.c"
+
+#undef LD
+#undef ST
+#undef XOR
+#undef LD_INOUT_LINE
+#undef LD_AND_XOR_LINE
+#undef ST_LINE
+#undef XOR_FUNC_NAME
+
+#endif /* CONFIG_CPU_HAS_LSX */
+
+#ifdef CONFIG_CPU_HAS_LASX
+
+#define LD(reg, base, offset)	\
+	"xvld $xr" #reg ", %[" #base "], " #offset "\n\t"
+#define ST(reg, base, offset)	\
+	"xvst $xr" #reg ", %[" #base "], " #offset "\n\t"
+#define XOR(dj, k)	"xvxor.v $xr" #dj ", $xr" #dj ", $xr" #k "\n\t"
+
+#define LD_INOUT_LINE(base)	\
+	LD(0, base, 0)		\
+	LD(1, base, 32)
+
+#define LD_AND_XOR_LINE(base)	\
+	LD(2, base, 0)		\
+	LD(3, base, 32)		\
+	XOR(0, 2)		\
+	XOR(1, 3)
+
+#define ST_LINE(base)		\
+	ST(0, base, 0)		\
+	ST(1, base, 32)
+
+#define XOR_FUNC_NAME(nr) __xor_lasx_##nr
+#include "xor_template.c"
+
+#undef LD
+#undef ST
+#undef XOR
+#undef LD_INOUT_LINE
+#undef LD_AND_XOR_LINE
+#undef ST_LINE
+#undef XOR_FUNC_NAME
+
+#endif /* CONFIG_CPU_HAS_LASX */

arch/loongarch/lib/xor_simd.h

+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Simple interface to link xor_simd.c and xor_simd_glue.c
+ *
+ * Separating these files ensures that no SIMD instructions are run outside of
+ * the kfpu critical section.
+ */
+
+#ifndef __LOONGARCH_LIB_XOR_SIMD_H
+#define __LOONGARCH_LIB_XOR_SIMD_H
+
+#ifdef CONFIG_CPU_HAS_LSX
+void __xor_lsx_2(unsigned long bytes, unsigned long * __restrict p1,
+		 const unsigned long * __restrict p2);
+void __xor_lsx_3(unsigned long bytes, unsigned long * __restrict p1,
+		 const unsigned long * __restrict p2, const unsigned long * __restrict p3);
+void __xor_lsx_4(unsigned long bytes, unsigned long * __restrict p1,
+		 const unsigned long * __restrict p2, const unsigned long * __restrict p3,
+		 const unsigned long * __restrict p4);
+void __xor_lsx_5(unsigned long bytes, unsigned long * __restrict p1,
+		 const unsigned long * __restrict p2, const unsigned long * __restrict p3,
+		 const unsigned long * __restrict p4, const unsigned long * __restrict p5);
+#endif /* CONFIG_CPU_HAS_LSX */
+
+#ifdef CONFIG_CPU_HAS_LASX
+void __xor_lasx_2(unsigned long bytes, unsigned long * __restrict p1,
+		  const unsigned long * __restrict p2);
+void __xor_lasx_3(unsigned long bytes, unsigned long * __restrict p1,
+		  const unsigned long * __restrict p2, const unsigned long * __restrict p3);
+void __xor_lasx_4(unsigned long bytes, unsigned long * __restrict p1,
+		  const unsigned long * __restrict p2, const unsigned long * __restrict p3,
+		  const unsigned long * __restrict p4);
+void __xor_lasx_5(unsigned long bytes, unsigned long * __restrict p1,
+		  const unsigned long * __restrict p2, const unsigned long * __restrict p3,
+		  const unsigned long * __restrict p4, const unsigned long * __restrict p5);
+#endif /* CONFIG_CPU_HAS_LASX */
+
+#endif /* __LOONGARCH_LIB_XOR_SIMD_H */

arch/loongarch/lib/xor_simd_glue.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * LoongArch SIMD XOR operations
+ *
+ * Copyright (C) 2023 WANG Xuerui <git@xen0n.name>
+ */
+
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <asm/fpu.h>
+#include <asm/xor_simd.h>
+#include "xor_simd.h"
+
+#define MAKE_XOR_GLUE_2(flavor)							\
+void xor_##flavor##_2(unsigned long bytes, unsigned long * __restrict p1,	\
+		      const unsigned long * __restrict p2)			\
+{										\
+	kernel_fpu_begin();							\
+	__xor_##flavor##_2(bytes, p1, p2);					\
+	kernel_fpu_end();							\
+}										\
+EXPORT_SYMBOL_GPL(xor_##flavor##_2)
+
+#define MAKE_XOR_GLUE_3(flavor)							\
+void xor_##flavor##_3(unsigned long bytes, unsigned long * __restrict p1,	\
+		      const unsigned long * __restrict p2,			\
+		      const unsigned long * __restrict p3)			\
+{										\
+	kernel_fpu_begin();							\
+	__xor_##flavor##_3(bytes, p1, p2, p3);					\
+	kernel_fpu_end();							\
+}										\
+EXPORT_SYMBOL_GPL(xor_##flavor##_3)
+
+#define MAKE_XOR_GLUE_4(flavor)							\
+void xor_##flavor##_4(unsigned long bytes, unsigned long * __restrict p1,	\
+		      const unsigned long * __restrict p2,			\
+		      const unsigned long * __restrict p3,			\
+		      const unsigned long * __restrict p4)			\
+{										\
+	kernel_fpu_begin();							\
+	__xor_##flavor##_4(bytes, p1, p2, p3, p4);				\
+	kernel_fpu_end();							\
+}										\
+EXPORT_SYMBOL_GPL(xor_##flavor##_4)
+
+#define MAKE_XOR_GLUE_5(flavor)							\
+void xor_##flavor##_5(unsigned long bytes, unsigned long * __restrict p1,	\
+		      const unsigned long * __restrict p2,			\
+		      const unsigned long * __restrict p3,			\
+		      const unsigned long * __restrict p4,			\
+		      const unsigned long * __restrict p5)			\
+{										\
+	kernel_fpu_begin();							\
+	__xor_##flavor##_5(bytes, p1, p2, p3, p4, p5);				\
+	kernel_fpu_end();							\
+}										\
+EXPORT_SYMBOL_GPL(xor_##flavor##_5)
+
+#define MAKE_XOR_GLUES(flavor)		\
+	MAKE_XOR_GLUE_2(flavor);	\
+	MAKE_XOR_GLUE_3(flavor);	\
+	MAKE_XOR_GLUE_4(flavor);	\
+	MAKE_XOR_GLUE_5(flavor)
+
+#ifdef CONFIG_CPU_HAS_LSX
+MAKE_XOR_GLUES(lsx);
+#endif
+
+#ifdef CONFIG_CPU_HAS_LASX
+MAKE_XOR_GLUES(lasx);
+#endif

arch/loongarch/lib/xor_template.c

+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2023 WANG Xuerui <git@xen0n.name>
+ *
+ * Template for XOR operations, instantiated in xor_simd.c.
+ *
+ * Expected preprocessor definitions:
+ *
+ * - LINE_WIDTH
+ * - XOR_FUNC_NAME(nr)
+ * - LD_INOUT_LINE(buf)
+ * - LD_AND_XOR_LINE(buf)
+ * - ST_LINE(buf)
+ */
+
+void XOR_FUNC_NAME(2)(unsigned long bytes,
+		      unsigned long * __restrict v1,
+		      const unsigned long * __restrict v2)
+{
+	unsigned long lines = bytes / LINE_WIDTH;
+
+	do {
+		__asm__ __volatile__ (
+			LD_INOUT_LINE(v1)
+			LD_AND_XOR_LINE(v2)
+			ST_LINE(v1)
+		: : [v1] "r"(v1), [v2] "r"(v2) : "memory"
+		);
+
+		v1 += LINE_WIDTH / sizeof(unsigned long);
+		v2 += LINE_WIDTH / sizeof(unsigned long);
+	} while (--lines > 0);
+}
+
+void XOR_FUNC_NAME(3)(unsigned long bytes,
+		      unsigned long * __restrict v1,
+		      const unsigned long * __restrict v2,
+		      const unsigned long * __restrict v3)
+{
+	unsigned long lines = bytes / LINE_WIDTH;
+
+	do {
+		__asm__ __volatile__ (
+			LD_INOUT_LINE(v1)
+			LD_AND_XOR_LINE(v2)
+			LD_AND_XOR_LINE(v3)
+			ST_LINE(v1)
+		: : [v1] "r"(v1), [v2] "r"(v2), [v3] "r"(v3) : "memory"
+		);
+
+		v1 += LINE_WIDTH / sizeof(unsigned long);
+		v2 += LINE_WIDTH / sizeof(unsigned long);
+		v3 += LINE_WIDTH / sizeof(unsigned long);
+	} while (--lines > 0);
+}
+
+void XOR_FUNC_NAME(4)(unsigned long bytes,
+		      unsigned long * __restrict v1,
+		      const unsigned long * __restrict v2,
+		      const unsigned long * __restrict v3,
+		      const unsigned long * __restrict v4)
+{
+	unsigned long lines = bytes / LINE_WIDTH;
+
+	do {
+		__asm__ __volatile__ (
+			LD_INOUT_LINE(v1)
+			LD_AND_XOR_LINE(v2)
+			LD_AND_XOR_LINE(v3)
+			LD_AND_XOR_LINE(v4)
+			ST_LINE(v1)
+		: : [v1] "r"(v1), [v2] "r"(v2), [v3] "r"(v3), [v4] "r"(v4)
+		: "memory"
+		);
+
+		v1 += LINE_WIDTH / sizeof(unsigned long);
+		v2 += LINE_WIDTH / sizeof(unsigned long);
+		v3 += LINE_WIDTH / sizeof(unsigned long);
+		v4 += LINE_WIDTH / sizeof(unsigned long);
+	} while (--lines > 0);
+}
+
+void XOR_FUNC_NAME(5)(unsigned long bytes,
+		      unsigned long * __restrict v1,
+		      const unsigned long * __restrict v2,
+		      const unsigned long * __restrict v3,
+		      const unsigned long * __restrict v4,
+		      const unsigned long * __restrict v5)
+{
+	unsigned long lines = bytes / LINE_WIDTH;
+
+	do {
+		__asm__ __volatile__ (
+			LD_INOUT_LINE(v1)
+			LD_AND_XOR_LINE(v2)
+			LD_AND_XOR_LINE(v3)
+			LD_AND_XOR_LINE(v4)
+			LD_AND_XOR_LINE(v5)
+			ST_LINE(v1)
+		: : [v1] "r"(v1), [v2] "r"(v2), [v3] "r"(v3), [v4] "r"(v4),
+		    [v5] "r"(v5) : "memory"
+		);
+
+		v1 += LINE_WIDTH / sizeof(unsigned long);
+		v2 += LINE_WIDTH / sizeof(unsigned long);
+		v3 += LINE_WIDTH / sizeof(unsigned long);
+		v4 += LINE_WIDTH / sizeof(unsigned long);
+		v5 += LINE_WIDTH / sizeof(unsigned long);
+	} while (--lines > 0);
+}