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 cpu;
  72         int err;
  73         u32 reg;
  74         u32 data[2];
  75 };
  76
  77 static void msr_smp_wrmsr(void *cmd_block)
  78 {
  79         struct msr_command *cmd = (struct msr_command *)cmd_block;
  80
  81         if (cmd->cpu == smp_processor_id())
  82                 cmd->err = wrmsr_eio(cmd->reg, cmd->data[0], cmd->data[1]);
  83 }
  84
  85 static void msr_smp_rdmsr(void *cmd_block)
  86 {
  87         struct msr_command *cmd = (struct msr_command *)cmd_block;
  88
  89         if (cmd->cpu == smp_processor_id())
  90                 cmd->err = rdmsr_eio(cmd->reg, &cmd->data[0], &cmd->data[1]);
  91 }
  92
  93 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
  94 {
  95         struct msr_command cmd;
  96         int ret;
  97
  98         preempt_disable();
  99         if (cpu == smp_processor_id()) {
 100                 ret = wrmsr_eio(reg, eax, edx);
 101         } else {
 102                 cmd.cpu = cpu;
 103                 cmd.reg = reg;
 104                 cmd.data[0] = eax;
 105                 cmd.data[1] = edx;
 106
 107                 smp_call_function(msr_smp_wrmsr, &cmd, 1, 1);
 108                 ret = cmd.err;
 109         }
 110         preempt_enable();
 111         return ret;
 112 }
 113
 114 static inline int do_rdmsr(int cpu, u32 reg, u32 * eax, u32 * edx)
 115 {
 116         struct msr_command cmd;
 117         int ret;
 118
 119         preempt_disable();
 120         if (cpu == smp_processor_id()) {
 121                 ret = rdmsr_eio(reg, eax, edx);
 122         } else {
 123                 cmd.cpu = cpu;
 124                 cmd.reg = reg;
 125
 126                 smp_call_function(msr_smp_rdmsr, &cmd, 1, 1);
 127
 128                 *eax = cmd.data[0];
 129                 *edx = cmd.data[1];
 130
 131                 ret = cmd.err;
 132         }
 133         preempt_enable();
 134         return ret;
 135 }
 136
 137 #else                           /* ! CONFIG_SMP */
 138
 139 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
 140 {
 141         return wrmsr_eio(reg, eax, edx);
 142 }
 143
 144 static inline int do_rdmsr(int cpu, u32 reg, u32 *eax, u32 *edx)
 145 {
 146         return rdmsr_eio(reg, eax, edx);
 147 }
 148
 149 #endif                          /* ! CONFIG_SMP */
 150
 151 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
 152 {
 153         loff_t ret = -EINVAL;
 154
 155         lock_kernel();
 156         switch (orig) {
 157         case 0:
 158                 file->f_pos = offset;
 159                 ret = file->f_pos;
 160                 break;
 161         case 1:
 162                 file->f_pos += offset;
 163                 ret = file->f_pos;
 164         }
 165         unlock_kernel();
 166         return ret;
 167 }
 168
 169 static ssize_t msr_read(struct file *file, char __user * buf,
 170                         size_t count, loff_t * ppos)
 171 {
 172         u32 __user *tmp = (u32 __user *) buf;
 173         u32 data[2];
 174         u32 reg = *ppos;
 175         int cpu = iminor(file->f_path.dentry->d_inode);
 176         int err;
 177
 178         if (count % 8)
 179                 return -EINVAL; /* Invalid chunk size */
 180
 181         for (; count; count -= 8) {
 182                 err = do_rdmsr(cpu, reg, &data[0], &data[1]);
 183                 if (err)
 184                         return err;
 185                 if (copy_to_user(tmp, &data, 8))
 186                         return -EFAULT;
 187                 tmp += 2;
 188         }
 189
 190         return ((char __user *)tmp) - buf;
 191 }
 192
 193 static ssize_t msr_write(struct file *file, const char __user *buf,
 194                          size_t count, loff_t *ppos)
 195 {
 196         const u32 __user *tmp = (const u32 __user *)buf;
 197         u32 data[2];
 198         u32 reg = *ppos;
 199         int cpu = iminor(file->f_path.dentry->d_inode);
 200         int err;
 201
 202         if (count % 8)
 203                 return -EINVAL; /* Invalid chunk size */
 204
 205         for (; count; count -= 8) {
 206                 if (copy_from_user(&data, tmp, 8))
 207                         return -EFAULT;
 208                 err = do_wrmsr(cpu, reg, data[0], data[1]);
 209                 if (err)
 210                         return err;
 211                 tmp += 2;
 212         }
 213
 214         return ((char __user *)tmp) - buf;
 215 }
 216
 217 static int msr_open(struct inode *inode, struct file *file)
 218 {
 219         unsigned int cpu = iminor(file->f_path.dentry->d_inode);
 220         struct cpuinfo_x86 *c = &(cpu_data)[cpu];
 221
 222         if (cpu >= NR_CPUS || !cpu_online(cpu))
 223                 return -ENXIO;  /* No such CPU */
 224         if (!cpu_has(c, X86_FEATURE_MSR))
 225                 return -EIO;    /* MSR not supported */
 226
 227         return 0;
 228 }
 229
 230 /*
 231  * File operations we support
 232  */
 233 static struct file_operations msr_fops = {
 234         .owner = THIS_MODULE,
 235         .llseek = msr_seek,
 236         .read = msr_read,
 237         .write = msr_write,
 238         .open = msr_open,
 239 };
 240
 241 static int msr_device_create(int i)
 242 {
 243         int err = 0;
 244         struct device *dev;
 245
 246         dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, i), "msr%d",i);
 247         if (IS_ERR(dev))
 248                 err = PTR_ERR(dev);
 249         return err;
 250 }
 251
 252 static int msr_class_cpu_callback(struct notifier_block *nfb,
 253                                 unsigned long action, void *hcpu)
 254 {
 255         unsigned int cpu = (unsigned long)hcpu;
 256
 257         switch (action) {
 258         case CPU_ONLINE:
 259                 msr_device_create(cpu);
 260                 break;
 261         case CPU_DEAD:
 262                 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 263                 break;
 264         }
 265         return NOTIFY_OK;
 266 }
 267
 268 static struct notifier_block __cpuinitdata msr_class_cpu_notifier =
 269 {
 270         .notifier_call = msr_class_cpu_callback,
 271 };
 272
 273 static int __init msr_init(void)
 274 {
 275         int i, err = 0;
 276         i = 0;
 277
 278         if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
 279                 printk(KERN_ERR "msr: unable to get major %d for msr\n",
 280                        MSR_MAJOR);
 281                 err = -EBUSY;
 282                 goto out;
 283         }
 284         msr_class = class_create(THIS_MODULE, "msr");
 285         if (IS_ERR(msr_class)) {
 286                 err = PTR_ERR(msr_class);
 287                 goto out_chrdev;
 288         }
 289         for_each_online_cpu(i) {
 290                 err = msr_device_create(i);
 291                 if (err != 0)
 292                         goto out_class;
 293         }
 294         register_hotcpu_notifier(&msr_class_cpu_notifier);
 295
 296         err = 0;
 297         goto out;
 298
 299 out_class:
 300         i = 0;
 301         for_each_online_cpu(i)
 302                 device_destroy(msr_class, MKDEV(MSR_MAJOR, i));
 303         class_destroy(msr_class);
 304 out_chrdev:
 305         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 306 out:
 307         return err;
 308 }
 309
 310 static void __exit msr_exit(void)
 311 {
 312         int cpu = 0;
 313         for_each_online_cpu(cpu)
 314                 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 315         class_destroy(msr_class);
 316         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 317         unregister_hotcpu_notifier(&msr_class_cpu_notifier);
 318 }
 319
 320 module_init(msr_init);
 321 module_exit(msr_exit)
 322
 323 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 324 MODULE_DESCRIPTION("x86 generic MSR driver");
 325 MODULE_LICENSE("GPL");