arch/x86/kernel/msr.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2000-2008 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;
  49         struct inode *inode = file->f_mapping->host;
  50
  51         mutex_lock(&inode->i_mutex);
  52         switch (orig) {
  53         case 0:
  54                 file->f_pos = offset;
  55                 ret = file->f_pos;
  56                 break;
  57         case 1:
  58                 file->f_pos += offset;
  59                 ret = file->f_pos;
  60                 break;
  61         default:
  62                 ret = -EINVAL;
  63         }
  64         mutex_unlock(&inode->i_mutex);
  65         return ret;
  66 }
  67
  68 static ssize_t msr_read(struct file *file, char __user *buf,
  69                         size_t count, loff_t *ppos)
  70 {
  71         u32 __user *tmp = (u32 __user *) buf;
  72         u32 data[2];
  73         u32 reg = *ppos;
  74         int cpu = iminor(file->f_path.dentry->d_inode);
  75         int err;
  76
  77         if (count % 8)
  78                 return -EINVAL; /* Invalid chunk size */
  79
  80         for (; count; count -= 8) {
  81                 err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
  82                 if (err)
  83                         return -EIO;
  84                 if (copy_to_user(tmp, &data, 8))
  85                         return -EFAULT;
  86                 tmp += 2;
  87         }
  88
  89         return ((char __user *)tmp) - buf;
  90 }
  91
  92 static ssize_t msr_write(struct file *file, const char __user *buf,
  93                          size_t count, loff_t *ppos)
  94 {
  95         const u32 __user *tmp = (const u32 __user *)buf;
  96         u32 data[2];
  97         u32 reg = *ppos;
  98         int cpu = iminor(file->f_path.dentry->d_inode);
  99         int err;
 100
 101         if (count % 8)
 102                 return -EINVAL; /* Invalid chunk size */
 103
 104         for (; count; count -= 8) {
 105                 if (copy_from_user(&data, tmp, 8))
 106                         return -EFAULT;
 107                 err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
 108                 if (err)
 109                         return -EIO;
 110                 tmp += 2;
 111         }
 112
 113         return ((char __user *)tmp) - buf;
 114 }
 115
 116 static int msr_open(struct inode *inode, struct file *file)
 117 {
 118         unsigned int cpu = iminor(file->f_path.dentry->d_inode);
 119         struct cpuinfo_x86 *c = &cpu_data(cpu);
 120
 121         if (cpu >= NR_CPUS || !cpu_online(cpu))
 122                 return -ENXIO;  /* No such CPU */
 123         if (!cpu_has(c, X86_FEATURE_MSR))
 124                 return -EIO;    /* MSR not supported */
 125
 126         return 0;
 127 }
 128
 129 /*
 130  * File operations we support
 131  */
 132 static const struct file_operations msr_fops = {
 133         .owner = THIS_MODULE,
 134         .llseek = msr_seek,
 135         .read = msr_read,
 136         .write = msr_write,
 137         .open = msr_open,
 138 };
 139
 140 static int __cpuinit msr_device_create(int cpu)
 141 {
 142         struct device *dev;
 143
 144         dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu),
 145                             "msr%d", cpu);
 146         return IS_ERR(dev) ? PTR_ERR(dev) : 0;
 147 }
 148
 149 static void msr_device_destroy(int cpu)
 150 {
 151         device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 152 }
 153
 154 static int __cpuinit msr_class_cpu_callback(struct notifier_block *nfb,
 155                                 unsigned long action, void *hcpu)
 156 {
 157         unsigned int cpu = (unsigned long)hcpu;
 158         int err = 0;
 159
 160         switch (action) {
 161         case CPU_UP_PREPARE:
 162                 err = msr_device_create(cpu);
 163                 break;
 164         case CPU_UP_CANCELED:
 165         case CPU_UP_CANCELED_FROZEN:
 166         case CPU_DEAD:
 167                 msr_device_destroy(cpu);
 168                 break;
 169         }
 170         return err ? NOTIFY_BAD : NOTIFY_OK;
 171 }
 172
 173 static struct notifier_block __refdata msr_class_cpu_notifier = {
 174         .notifier_call = msr_class_cpu_callback,
 175 };
 176
 177 static int __init msr_init(void)
 178 {
 179         int i, err = 0;
 180         i = 0;
 181
 182         if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
 183                 printk(KERN_ERR "msr: unable to get major %d for msr\n",
 184                        MSR_MAJOR);
 185                 err = -EBUSY;
 186                 goto out;
 187         }
 188         msr_class = class_create(THIS_MODULE, "msr");
 189         if (IS_ERR(msr_class)) {
 190                 err = PTR_ERR(msr_class);
 191                 goto out_chrdev;
 192         }
 193         for_each_online_cpu(i) {
 194                 err = msr_device_create(i);
 195                 if (err != 0)
 196                         goto out_class;
 197         }
 198         register_hotcpu_notifier(&msr_class_cpu_notifier);
 199
 200         err = 0;
 201         goto out;
 202
 203 out_class:
 204         i = 0;
 205         for_each_online_cpu(i)
 206                 msr_device_destroy(i);
 207         class_destroy(msr_class);
 208 out_chrdev:
 209         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 210 out:
 211         return err;
 212 }
 213
 214 static void __exit msr_exit(void)
 215 {
 216         int cpu = 0;
 217         for_each_online_cpu(cpu)
 218                 msr_device_destroy(cpu);
 219         class_destroy(msr_class);
 220         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 221         unregister_hotcpu_notifier(&msr_class_cpu_notifier);
 222 }
 223
 224 module_init(msr_init);
 225 module_exit(msr_exit)
 226
 227 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 228 MODULE_DESCRIPTION("x86 generic MSR driver");
 229 MODULE_LICENSE("GPL");