crypto/xor.c

   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.  */
  24 static struct xor_block_template *active_template;
  25
  26 void
  27 xor_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 }
  52 EXPORT_SYMBOL(xor_blocks);
  53
  54 /* Set of all registered templates.  */
  55 static struct xor_block_template *__initdata template_list;
  56
  57 #define BENCH_SIZE (PAGE_SIZE)
  58
  59 static void __init
  60 do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
  61 {
  62         int speed;
  63         unsigned long now, j;
  64         int i, count, max;
  65
  66         tmpl->next = template_list;
  67         template_list = tmpl;
  68
  69         preempt_disable();
  70
  71         /*
  72          * Count the number of XORs done during a whole jiffy, and use
  73          * this to calculate the speed of checksumming.  We use a 2-page
  74          * allocation to have guaranteed color L1-cache layout.
  75          */
  76         max = 0;
  77         for (i = 0; i < 5; i++) {
  78                 j = jiffies;
  79                 count = 0;
  80                 while ((now = jiffies) == j)
  81                         cpu_relax();
  82                 while (time_before(jiffies, now + 1)) {
  83                         mb(); /* prevent loop optimzation */
  84                         tmpl->do_2(BENCH_SIZE, b1, b2);
  85                         mb();
  86                         count++;
  87                         mb();
  88                 }
  89                 if (count > max)
  90                         max = count;
  91         }
  92
  93         preempt_enable();
  94
  95         speed = max * (HZ * BENCH_SIZE / 1024);
  96         tmpl->speed = speed;
  97
  98         printk(KERN_INFO "   %-10s: %5d.%03d MB/sec\n", tmpl->name,
  99                speed / 1000, speed % 1000);
 100 }
 101
 102 static int __init
 103 calibrate_xor_blocks(void)
 104 {
 105         void *b1, *b2;
 106         struct xor_block_template *f, *fastest;
 107
 108         fastest = XOR_SELECT_TEMPLATE(NULL);
 109
 110         if (fastest) {
 111                 printk(KERN_INFO "xor: automatically using best "
 112                                  "checksumming function   %-10s\n",
 113                        fastest->name);
 114                 goto out;
 115         }
 116
 117         b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
 118         if (!b1) {
 119                 printk(KERN_WARNING "xor: Yikes!  No memory available.\n");
 120                 return -ENOMEM;
 121         }
 122         b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
 123
 124         /*
 125          * If this arch/cpu has a short-circuited selection, don't loop through
 126          * all the possible functions, just test the best one
 127          */
 128
 129 #define xor_speed(templ)        do_xor_speed((templ), b1, b2)
 130
 131         printk(KERN_INFO "xor: measuring software checksum speed\n");
 132         XOR_TRY_TEMPLATES;
 133         fastest = template_list;
 134         for (f = fastest; f; f = f->next)
 135                 if (f->speed > fastest->speed)
 136                         fastest = f;
 137
 138         printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)\n",
 139                fastest->name, fastest->speed / 1000, fastest->speed % 1000);
 140
 141 #undef xor_speed
 142
 143         free_pages((unsigned long)b1, 2);
 144 out:
 145         active_template = fastest;
 146         return 0;
 147 }
 148
 149 static __exit void xor_exit(void) { }
 150
 151 MODULE_LICENSE("GPL");
 152
 153 /* when built-in xor.o must initialize before drivers/md/md.o */
 154 core_initcall(calibrate_xor_blocks);
 155 module_exit(xor_exit);