1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * xor.c : Multiple Devices driver for Linux
4 *
5 * Copyright (C) 1996, 1997, 1998, 1999, 2000,
6 * Ingo Molnar, Matti Aarnio, Jakub Jelinek, Richard Henderson.
7 *
8 * Dispatch optimized RAID-5 checksumming functions.
9 */
10
11#define BH_TRACE 0
12#include <linux/module.h>
13#include <linux/gfp.h>
14#include <linux/raid/xor.h>
15#include <linux/jiffies.h>
16#include <linux/preempt.h>
17#include <asm/xor.h>
18
19#ifndef XOR_SELECT_TEMPLATE
20#define XOR_SELECT_TEMPLATE(x) (x)
21#endif
22
23/* The xor routines to use. */
24static struct xor_block_template *active_template;
25
26void
27xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)
28{
29 unsigned long *p1, *p2, *p3, *p4;
30
31 p1 = (unsigned long *) srcs[0];
32 if (src_count == 1) {
33 active_template->do_2(bytes, dest, p1);
34 return;
35 }
36
37 p2 = (unsigned long *) srcs[1];
38 if (src_count == 2) {
39 active_template->do_3(bytes, dest, p1, p2);
40 return;
41 }
42
43 p3 = (unsigned long *) srcs[2];
44 if (src_count == 3) {
45 active_template->do_4(bytes, dest, p1, p2, p3);
46 return;
47 }
48
49 p4 = (unsigned long *) srcs[3];
50 active_template->do_5(bytes, dest, p1, p2, p3, p4);
51}
52EXPORT_SYMBOL(xor_blocks);
53
54/* Set of all registered templates. */
55static struct xor_block_template *__initdata template_list;
56
57#ifndef MODULE
58static void __init do_xor_register(struct xor_block_template *tmpl)
59{
60 tmpl->next = template_list;
61 template_list = tmpl;
62}
63
64static int __init register_xor_blocks(void)
65{
66 active_template = XOR_SELECT_TEMPLATE(NULL);
67
68 if (!active_template) {
69#define xor_speed do_xor_register
70 // register all the templates and pick the first as the default
71 XOR_TRY_TEMPLATES;
72#undef xor_speed
73 active_template = template_list;
74 }
75 return 0;
76}
77#endif
78
79#define BENCH_SIZE 4096
80#define REPS 800U
81
82static void __init
83do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
84{
85 int speed;
86 unsigned long reps;
87 ktime_t min, start, t0;
88
89 tmpl->next = template_list;
90 template_list = tmpl;
91
92 preempt_disable();
93
94 reps = 0;
95 t0 = ktime_get();
96 /* delay start until time has advanced */
97 while ((start = ktime_get()) == t0)
98 cpu_relax();
99 do {
100 mb(); /* prevent loop optimization */
101 tmpl->do_2(BENCH_SIZE, b1, b2);
102 mb();
103 } while (reps++ < REPS || (t0 = ktime_get()) == start);
104 min = ktime_sub(t0, start);
105
106 preempt_enable();
107
108 // bytes/ns == GB/s, multiply by 1000 to get MB/s [not MiB/s]
109 speed = (1000 * reps * BENCH_SIZE) / (unsigned int)ktime_to_ns(kt: min);
110 tmpl->speed = speed;
111
112 pr_info(" %-16s: %5d MB/sec\n", tmpl->name, speed);
113}
114
115static int __init
116calibrate_xor_blocks(void)
117{
118 void *b1, *b2;
119 struct xor_block_template *f, *fastest;
120
121 fastest = XOR_SELECT_TEMPLATE(NULL);
122
123 if (fastest) {
124 printk(KERN_INFO "xor: automatically using best "
125 "checksumming function %-10s\n",
126 fastest->name);
127 goto out;
128 }
129
130 b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
131 if (!b1) {
132 printk(KERN_WARNING "xor: Yikes! No memory available.\n");
133 return -ENOMEM;
134 }
135 b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
136
137 /*
138 * If this arch/cpu has a short-circuited selection, don't loop through
139 * all the possible functions, just test the best one
140 */
141
142#define xor_speed(templ) do_xor_speed((templ), b1, b2)
143
144 printk(KERN_INFO "xor: measuring software checksum speed\n");
145 template_list = NULL;
146 XOR_TRY_TEMPLATES;
147 fastest = template_list;
148 for (f = fastest; f; f = f->next)
149 if (f->speed > fastest->speed)
150 fastest = f;
151
152 pr_info("xor: using function: %s (%d MB/sec)\n",
153 fastest->name, fastest->speed);
154
155#undef xor_speed
156
157 free_pages(addr: (unsigned long)b1, order: 2);
158out:
159 active_template = fastest;
160 return 0;
161}
162
163static __exit void xor_exit(void) { }
164
165MODULE_DESCRIPTION("RAID-5 checksumming functions");
166MODULE_LICENSE("GPL");
167
168#ifndef MODULE
169/* when built-in xor.o must initialize before drivers/md/md.o */
170core_initcall(register_xor_blocks);
171#endif
172
173module_init(calibrate_xor_blocks);
174module_exit(xor_exit);
175

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source code of linux/crypto/xor.c