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 msr_device_create(int i)
 137 {
 138         int err = 0;
 139         struct device *dev;
 140
 141         dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, i), "msr%d",i);
 142         if (IS_ERR(dev))
 143                 err = PTR_ERR(dev);
 144         return err;
 145 }
 146
 147 static int msr_class_cpu_callback(struct notifier_block *nfb,
 148                                 unsigned long action, void *hcpu)
 149 {
 150         unsigned int cpu = (unsigned long)hcpu;
 151
 152         switch (action) {
 153         case CPU_ONLINE:
 154         case CPU_ONLINE_FROZEN:
 155                 msr_device_create(cpu);
 156                 break;
 157         case CPU_DEAD:
 158         case CPU_DEAD_FROZEN:
 159                 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 160                 break;
 161         }
 162         return NOTIFY_OK;
 163 }
 164
 165 static struct notifier_block __cpuinitdata msr_class_cpu_notifier =
 166 {
 167         .notifier_call = msr_class_cpu_callback,
 168 };
 169
 170 static int __init msr_init(void)
 171 {
 172         int i, err = 0;
 173         i = 0;
 174
 175         if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
 176                 printk(KERN_ERR "msr: unable to get major %d for msr\n",
 177                        MSR_MAJOR);
 178                 err = -EBUSY;
 179                 goto out;
 180         }
 181         msr_class = class_create(THIS_MODULE, "msr");
 182         if (IS_ERR(msr_class)) {
 183                 err = PTR_ERR(msr_class);
 184                 goto out_chrdev;
 185         }
 186         for_each_online_cpu(i) {
 187                 err = msr_device_create(i);
 188                 if (err != 0)
 189                         goto out_class;
 190         }
 191         register_hotcpu_notifier(&msr_class_cpu_notifier);
 192
 193         err = 0;
 194         goto out;
 195
 196 out_class:
 197         i = 0;
 198         for_each_online_cpu(i)
 199                 device_destroy(msr_class, MKDEV(MSR_MAJOR, i));
 200         class_destroy(msr_class);
 201 out_chrdev:
 202         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 203 out:
 204         return err;
 205 }
 206
 207 static void __exit msr_exit(void)
 208 {
 209         int cpu = 0;
 210         for_each_online_cpu(cpu)
 211                 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 212         class_destroy(msr_class);
 213         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 214         unregister_hotcpu_notifier(&msr_class_cpu_notifier);
 215 }
 216
 217 module_init(msr_init);
 218 module_exit(msr_exit)
 219
 220 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 221 MODULE_DESCRIPTION("x86 generic MSR driver");
 222 MODULE_LICENSE("GPL");