arch/i386/kernel/msr.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2000 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   This program is free software; you can redistribute it and/or modify
   6  *   it under the terms of the GNU General Public License as published by
   7  *   the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
   8  *   USA; either version 2 of the License, or (at your option) any later
   9  *   version; incorporated herein by reference.
  10  *
  11  * ----------------------------------------------------------------------- */
  12
  13 /*
  14  * msr.c
  15  *
  16  * x86 MSR access device
  17  *
  18  * This device is accessed by lseek() to the appropriate register number
  19  * and then read/write in chunks of 8 bytes.  A larger size means multiple
  20  * reads or writes of the same register.
  21  *
  22  * This driver uses /dev/cpu/%d/msr where %d is the minor number, and on
  23  * an SMP box will direct the access to CPU %d.
  24  */
  25
  26 #include <linux/module.h>
  27
  28 #include <linux/types.h>
  29 #include <linux/errno.h>
  30 #include <linux/fcntl.h>
  31 #include <linux/init.h>
  32 #include <linux/poll.h>
  33 #include <linux/smp.h>
  34 #include <linux/smp_lock.h>
  35 #include <linux/major.h>
  36 #include <linux/fs.h>
  37 #include <linux/device.h>
  38 #include <linux/cpu.h>
  39 #include <linux/notifier.h>
  40
  41 #include <asm/processor.h>
  42 #include <asm/msr.h>
  43 #include <asm/uaccess.h>
  44 #include <asm/system.h>
  45
  46 static struct class *msr_class;
  47
  48 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
  49 {
  50         loff_t ret = -EINVAL;
  51
  52         lock_kernel();
  53         switch (orig) {
  54         case 0:
  55                 file->f_pos = offset;
  56                 ret = file->f_pos;
  57                 break;
  58         case 1:
  59                 file->f_pos += offset;
  60                 ret = file->f_pos;
  61         }
  62         unlock_kernel();
  63         return ret;
  64 }
  65
  66 static ssize_t msr_read(struct file *file, char __user * buf,
  67                         size_t count, loff_t * ppos)
  68 {
  69         u32 __user *tmp = (u32 __user *) buf;
  70         u32 data[2];
  71         u32 reg = *ppos;
  72         int cpu = iminor(file->f_path.dentry->d_inode);
  73         int err;
  74
  75         if (count % 8)
  76                 return -EINVAL; /* Invalid chunk size */
  77
  78         for (; count; count -= 8) {
  79                 err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
  80                 if (err)
  81                         return -EIO;
  82                 if (copy_to_user(tmp, &data, 8))
  83                         return -EFAULT;
  84                 tmp += 2;
  85         }
  86
  87         return ((char __user *)tmp) - buf;
  88 }
  89
  90 static ssize_t msr_write(struct file *file, const char __user *buf,
  91                          size_t count, loff_t *ppos)
  92 {
  93         const u32 __user *tmp = (const u32 __user *)buf;
  94         u32 data[2];
  95         u32 reg = *ppos;
  96         int cpu = iminor(file->f_path.dentry->d_inode);
  97         int err;
  98
  99         if (count % 8)
 100                 return -EINVAL; /* Invalid chunk size */
 101
 102         for (; count; count -= 8) {
 103                 if (copy_from_user(&data, tmp, 8))
 104                         return -EFAULT;
 105                 err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
 106                 if (err)
 107                         return -EIO;
 108                 tmp += 2;
 109         }
 110
 111         return ((char __user *)tmp) - buf;
 112 }
 113
 114 static int msr_open(struct inode *inode, struct file *file)
 115 {
 116         unsigned int cpu = iminor(file->f_path.dentry->d_inode);
 117         struct cpuinfo_x86 *c = &(cpu_data)[cpu];
 118
 119         if (cpu >= NR_CPUS || !cpu_online(cpu))
 120                 return -ENXIO;  /* No such CPU */
 121         if (!cpu_has(c, X86_FEATURE_MSR))
 122                 return -EIO;    /* MSR not supported */
 123
 124         return 0;
 125 }
 126
 127 /*
 128  * File operations we support
 129  */
 130 static const struct file_operations msr_fops = {
 131         .owner = THIS_MODULE,
 132         .llseek = msr_seek,
 133         .read = msr_read,
 134         .write = msr_write,
 135         .open = msr_open,
 136 };
 137
 138 static int msr_device_create(int i)
 139 {
 140         int err = 0;
 141         struct device *dev;
 142
 143         dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, i), "msr%d",i);
 144         if (IS_ERR(dev))
 145                 err = PTR_ERR(dev);
 146         return err;
 147 }
 148
 149 static int msr_class_cpu_callback(struct notifier_block *nfb,
 150                                 unsigned long action, void *hcpu)
 151 {
 152         unsigned int cpu = (unsigned long)hcpu;
 153
 154         switch (action) {
 155         case CPU_ONLINE:
 156         case CPU_ONLINE_FROZEN:
 157                 msr_device_create(cpu);
 158                 break;
 159         case CPU_DEAD:
 160         case CPU_DEAD_FROZEN:
 161                 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 162                 break;
 163         }
 164         return NOTIFY_OK;
 165 }
 166
 167 static struct notifier_block __cpuinitdata msr_class_cpu_notifier =
 168 {
 169         .notifier_call = msr_class_cpu_callback,
 170 };
 171
 172 static int __init msr_init(void)
 173 {
 174         int i, err = 0;
 175         i = 0;
 176
 177         if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
 178                 printk(KERN_ERR "msr: unable to get major %d for msr\n",
 179                        MSR_MAJOR);
 180                 err = -EBUSY;
 181                 goto out;
 182         }
 183         msr_class = class_create(THIS_MODULE, "msr");
 184         if (IS_ERR(msr_class)) {
 185                 err = PTR_ERR(msr_class);
 186                 goto out_chrdev;
 187         }
 188         for_each_online_cpu(i) {
 189                 err = msr_device_create(i);
 190                 if (err != 0)
 191                         goto out_class;
 192         }
 193         register_hotcpu_notifier(&msr_class_cpu_notifier);
 194
 195         err = 0;
 196         goto out;
 197
 198 out_class:
 199         i = 0;
 200         for_each_online_cpu(i)
 201                 device_destroy(msr_class, MKDEV(MSR_MAJOR, i));
 202         class_destroy(msr_class);
 203 out_chrdev:
 204         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 205 out:
 206         return err;
 207 }
 208
 209 static void __exit msr_exit(void)
 210 {
 211         int cpu = 0;
 212         for_each_online_cpu(cpu)
 213                 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 214         class_destroy(msr_class);
 215         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 216         unregister_hotcpu_notifier(&msr_class_cpu_notifier);
 217 }
 218
 219 module_init(msr_init);
 220 module_exit(msr_exit)
 221
 222 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 223 MODULE_DESCRIPTION("x86 generic MSR driver");
 224 MODULE_LICENSE("GPL");