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