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 inline int wrmsr_eio(u32 reg, u32 eax, u32 edx)
  49 {
  50         int err;
  51
  52         err = wrmsr_safe(reg, eax, edx);
  53         if (err)
  54                 err = -EIO;
  55         return err;
  56 }
  57
  58 static inline int rdmsr_eio(u32 reg, u32 *eax, u32 *edx)
  59 {
  60         int err;
  61
  62         err = rdmsr_safe(reg, eax, edx);
  63         if (err)
  64                 err = -EIO;
  65         return err;
  66 }
  67
  68 #ifdef CONFIG_SMP
  69
  70 struct msr_command {
  71         int err;
  72         u32 reg;
  73         u32 data[2];
  74 };
  75
  76 static void msr_smp_wrmsr(void *cmd_block)
  77 {
  78         struct msr_command *cmd = (struct msr_command *)cmd_block;
  79
  80         cmd->err = wrmsr_eio(cmd->reg, cmd->data[0], cmd->data[1]);
  81 }
  82
  83 static void msr_smp_rdmsr(void *cmd_block)
  84 {
  85         struct msr_command *cmd = (struct msr_command *)cmd_block;
  86
  87         cmd->err = rdmsr_eio(cmd->reg, &cmd->data[0], &cmd->data[1]);
  88 }
  89
  90 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
  91 {
  92         struct msr_command cmd;
  93         int ret;
  94
  95         preempt_disable();
  96         if (cpu == smp_processor_id()) {
  97                 ret = wrmsr_eio(reg, eax, edx);
  98         } else {
  99                 cmd.reg = reg;
 100                 cmd.data[0] = eax;
 101                 cmd.data[1] = edx;
 102
 103                 smp_call_function_single(cpu, msr_smp_wrmsr, &cmd, 1, 1);
 104                 ret = cmd.err;
 105         }
 106         preempt_enable();
 107         return ret;
 108 }
 109
 110 static inline int do_rdmsr(int cpu, u32 reg, u32 * eax, u32 * edx)
 111 {
 112         struct msr_command cmd;
 113         int ret;
 114
 115         preempt_disable();
 116         if (cpu == smp_processor_id()) {
 117                 ret = rdmsr_eio(reg, eax, edx);
 118         } else {
 119                 cmd.reg = reg;
 120
 121                 smp_call_function_single(cpu, msr_smp_rdmsr, &cmd, 1, 1);
 122
 123                 *eax = cmd.data[0];
 124                 *edx = cmd.data[1];
 125
 126                 ret = cmd.err;
 127         }
 128         preempt_enable();
 129         return ret;
 130 }
 131
 132 #else                           /* ! CONFIG_SMP */
 133
 134 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
 135 {
 136         return wrmsr_eio(reg, eax, edx);
 137 }
 138
 139 static inline int do_rdmsr(int cpu, u32 reg, u32 *eax, u32 *edx)
 140 {
 141         return rdmsr_eio(reg, eax, edx);
 142 }
 143
 144 #endif                          /* ! CONFIG_SMP */
 145
 146 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
 147 {
 148         loff_t ret = -EINVAL;
 149
 150         lock_kernel();
 151         switch (orig) {
 152         case 0:
 153                 file->f_pos = offset;
 154                 ret = file->f_pos;
 155                 break;
 156         case 1:
 157                 file->f_pos += offset;
 158                 ret = file->f_pos;
 159         }
 160         unlock_kernel();
 161         return ret;
 162 }
 163
 164 static ssize_t msr_read(struct file *file, char __user * buf,
 165                         size_t count, loff_t * ppos)
 166 {
 167         u32 __user *tmp = (u32 __user *) buf;
 168         u32 data[2];
 169         u32 reg = *ppos;
 170         int cpu = iminor(file->f_path.dentry->d_inode);
 171         int err;
 172
 173         if (count % 8)
 174                 return -EINVAL; /* Invalid chunk size */
 175
 176         for (; count; count -= 8) {
 177                 err = do_rdmsr(cpu, reg, &data[0], &data[1]);
 178                 if (err)
 179                         return err;
 180                 if (copy_to_user(tmp, &data, 8))
 181                         return -EFAULT;
 182                 tmp += 2;
 183         }
 184
 185         return ((char __user *)tmp) - buf;
 186 }
 187
 188 static ssize_t msr_write(struct file *file, const char __user *buf,
 189                          size_t count, loff_t *ppos)
 190 {
 191         const u32 __user *tmp = (const u32 __user *)buf;
 192         u32 data[2];
 193         u32 reg = *ppos;
 194         int cpu = iminor(file->f_path.dentry->d_inode);
 195         int err;
 196
 197         if (count % 8)
 198                 return -EINVAL; /* Invalid chunk size */
 199
 200         for (; count; count -= 8) {
 201                 if (copy_from_user(&data, tmp, 8))
 202                         return -EFAULT;
 203                 err = do_wrmsr(cpu, reg, data[0], data[1]);
 204                 if (err)
 205                         return err;
 206                 tmp += 2;
 207         }
 208
 209         return ((char __user *)tmp) - buf;
 210 }
 211
 212 static int msr_open(struct inode *inode, struct file *file)
 213 {
 214         unsigned int cpu = iminor(file->f_path.dentry->d_inode);
 215         struct cpuinfo_x86 *c = &(cpu_data)[cpu];
 216
 217         if (cpu >= NR_CPUS || !cpu_online(cpu))
 218                 return -ENXIO;  /* No such CPU */
 219         if (!cpu_has(c, X86_FEATURE_MSR))
 220                 return -EIO;    /* MSR not supported */
 221
 222         return 0;
 223 }
 224
 225 /*
 226  * File operations we support
 227  */
 228 static const struct file_operations msr_fops = {
 229         .owner = THIS_MODULE,
 230         .llseek = msr_seek,
 231         .read = msr_read,
 232         .write = msr_write,
 233         .open = msr_open,
 234 };
 235
 236 static int msr_device_create(int i)
 237 {
 238         int err = 0;
 239         struct device *dev;
 240
 241         dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, i), "msr%d",i);
 242         if (IS_ERR(dev))
 243                 err = PTR_ERR(dev);
 244         return err;
 245 }
 246
 247 static int msr_class_cpu_callback(struct notifier_block *nfb,
 248                                 unsigned long action, void *hcpu)
 249 {
 250         unsigned int cpu = (unsigned long)hcpu;
 251
 252         switch (action) {
 253         case CPU_ONLINE:
 254                 msr_device_create(cpu);
 255                 break;
 256         case CPU_DEAD:
 257                 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 258                 break;
 259         }
 260         return NOTIFY_OK;
 261 }
 262
 263 static struct notifier_block __cpuinitdata msr_class_cpu_notifier =
 264 {
 265         .notifier_call = msr_class_cpu_callback,
 266 };
 267
 268 static int __init msr_init(void)
 269 {
 270         int i, err = 0;
 271         i = 0;
 272
 273         if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
 274                 printk(KERN_ERR "msr: unable to get major %d for msr\n",
 275                        MSR_MAJOR);
 276                 err = -EBUSY;
 277                 goto out;
 278         }
 279         msr_class = class_create(THIS_MODULE, "msr");
 280         if (IS_ERR(msr_class)) {
 281                 err = PTR_ERR(msr_class);
 282                 goto out_chrdev;
 283         }
 284         for_each_online_cpu(i) {
 285                 err = msr_device_create(i);
 286                 if (err != 0)
 287                         goto out_class;
 288         }
 289         register_hotcpu_notifier(&msr_class_cpu_notifier);
 290
 291         err = 0;
 292         goto out;
 293
 294 out_class:
 295         i = 0;
 296         for_each_online_cpu(i)
 297                 device_destroy(msr_class, MKDEV(MSR_MAJOR, i));
 298         class_destroy(msr_class);
 299 out_chrdev:
 300         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 301 out:
 302         return err;
 303 }
 304
 305 static void __exit msr_exit(void)
 306 {
 307         int cpu = 0;
 308         for_each_online_cpu(cpu)
 309                 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 310         class_destroy(msr_class);
 311         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 312         unregister_hotcpu_notifier(&msr_class_cpu_notifier);
 313 }
 314
 315 module_init(msr_init);
 316 module_exit(msr_exit)
 317
 318 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 319 MODULE_DESCRIPTION("x86 generic MSR driver");
 320 MODULE_LICENSE("GPL");