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 #include <linux/config.h>
  28
  29 #include <linux/types.h>
  30 #include <linux/errno.h>
  31 #include <linux/fcntl.h>
  32 #include <linux/init.h>
  33 #include <linux/poll.h>
  34 #include <linux/smp.h>
  35 #include <linux/smp_lock.h>
  36 #include <linux/major.h>
  37 #include <linux/fs.h>
  38 #include <linux/device.h>
  39 #include <linux/cpu.h>
  40 #include <linux/notifier.h>
  41
  42 #include <asm/processor.h>
  43 #include <asm/msr.h>
  44 #include <asm/uaccess.h>
  45 #include <asm/system.h>
  46
  47 static struct class *msr_class;
  48
  49 static inline int wrmsr_eio(u32 reg, u32 eax, u32 edx)
  50 {
  51         int err;
  52
  53         err = wrmsr_safe(reg, eax, edx);
  54         if (err)
  55                 err = -EIO;
  56         return err;
  57 }
  58
  59 static inline int rdmsr_eio(u32 reg, u32 *eax, u32 *edx)
  60 {
  61         int err;
  62
  63         err = rdmsr_safe(reg, eax, edx);
  64         if (err)
  65                 err = -EIO;
  66         return err;
  67 }
  68
  69 #ifdef CONFIG_SMP
  70
  71 struct msr_command {
  72         int cpu;
  73         int err;
  74         u32 reg;
  75         u32 data[2];
  76 };
  77
  78 static void msr_smp_wrmsr(void *cmd_block)
  79 {
  80         struct msr_command *cmd = (struct msr_command *)cmd_block;
  81
  82         if (cmd->cpu == smp_processor_id())
  83                 cmd->err = wrmsr_eio(cmd->reg, cmd->data[0], cmd->data[1]);
  84 }
  85
  86 static void msr_smp_rdmsr(void *cmd_block)
  87 {
  88         struct msr_command *cmd = (struct msr_command *)cmd_block;
  89
  90         if (cmd->cpu == smp_processor_id())
  91                 cmd->err = rdmsr_eio(cmd->reg, &cmd->data[0], &cmd->data[1]);
  92 }
  93
  94 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
  95 {
  96         struct msr_command cmd;
  97         int ret;
  98
  99         preempt_disable();
 100         if (cpu == smp_processor_id()) {
 101                 ret = wrmsr_eio(reg, eax, edx);
 102         } else {
 103                 cmd.cpu = cpu;
 104                 cmd.reg = reg;
 105                 cmd.data[0] = eax;
 106                 cmd.data[1] = edx;
 107
 108                 smp_call_function(msr_smp_wrmsr, &cmd, 1, 1);
 109                 ret = cmd.err;
 110         }
 111         preempt_enable();
 112         return ret;
 113 }
 114
 115 static inline int do_rdmsr(int cpu, u32 reg, u32 * eax, u32 * edx)
 116 {
 117         struct msr_command cmd;
 118         int ret;
 119
 120         preempt_disable();
 121         if (cpu == smp_processor_id()) {
 122                 ret = rdmsr_eio(reg, eax, edx);
 123         } else {
 124                 cmd.cpu = cpu;
 125                 cmd.reg = reg;
 126
 127                 smp_call_function(msr_smp_rdmsr, &cmd, 1, 1);
 128
 129                 *eax = cmd.data[0];
 130                 *edx = cmd.data[1];
 131
 132                 ret = cmd.err;
 133         }
 134         preempt_enable();
 135         return ret;
 136 }
 137
 138 #else                           /* ! CONFIG_SMP */
 139
 140 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
 141 {
 142         return wrmsr_eio(reg, eax, edx);
 143 }
 144
 145 static inline int do_rdmsr(int cpu, u32 reg, u32 *eax, u32 *edx)
 146 {
 147         return rdmsr_eio(reg, eax, edx);
 148 }
 149
 150 #endif                          /* ! CONFIG_SMP */
 151
 152 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
 153 {
 154         loff_t ret = -EINVAL;
 155
 156         lock_kernel();
 157         switch (orig) {
 158         case 0:
 159                 file->f_pos = offset;
 160                 ret = file->f_pos;
 161                 break;
 162         case 1:
 163                 file->f_pos += offset;
 164                 ret = file->f_pos;
 165         }
 166         unlock_kernel();
 167         return ret;
 168 }
 169
 170 static ssize_t msr_read(struct file *file, char __user * buf,
 171                         size_t count, loff_t * ppos)
 172 {
 173         u32 __user *tmp = (u32 __user *) buf;
 174         u32 data[2];
 175         u32 reg = *ppos;
 176         int cpu = iminor(file->f_dentry->d_inode);
 177         int err;
 178
 179         if (count % 8)
 180                 return -EINVAL; /* Invalid chunk size */
 181
 182         for (; count; count -= 8) {
 183                 err = do_rdmsr(cpu, reg, &data[0], &data[1]);
 184                 if (err)
 185                         return err;
 186                 if (copy_to_user(tmp, &data, 8))
 187                         return -EFAULT;
 188                 tmp += 2;
 189         }
 190
 191         return ((char __user *)tmp) - buf;
 192 }
 193
 194 static ssize_t msr_write(struct file *file, const char __user *buf,
 195                          size_t count, loff_t *ppos)
 196 {
 197         const u32 __user *tmp = (const u32 __user *)buf;
 198         u32 data[2];
 199         size_t rv;
 200         u32 reg = *ppos;
 201         int cpu = iminor(file->f_dentry->d_inode);
 202         int err;
 203
 204         if (count % 8)
 205                 return -EINVAL; /* Invalid chunk size */
 206
 207         for (rv = 0; count; count -= 8) {
 208                 if (copy_from_user(&data, tmp, 8))
 209                         return -EFAULT;
 210                 err = do_wrmsr(cpu, reg, data[0], data[1]);
 211                 if (err)
 212                         return err;
 213                 tmp += 2;
 214         }
 215
 216         return ((char __user *)tmp) - buf;
 217 }
 218
 219 static int msr_open(struct inode *inode, struct file *file)
 220 {
 221         unsigned int cpu = iminor(file->f_dentry->d_inode);
 222         struct cpuinfo_x86 *c = &(cpu_data)[cpu];
 223
 224         if (cpu >= NR_CPUS || !cpu_online(cpu))
 225                 return -ENXIO;  /* No such CPU */
 226         if (!cpu_has(c, X86_FEATURE_MSR))
 227                 return -EIO;    /* MSR not supported */
 228
 229         return 0;
 230 }
 231
 232 /*
 233  * File operations we support
 234  */
 235 static struct file_operations msr_fops = {
 236         .owner = THIS_MODULE,
 237         .llseek = msr_seek,
 238         .read = msr_read,
 239         .write = msr_write,
 240         .open = msr_open,
 241 };
 242
 243 static int msr_class_device_create(int i)
 244 {
 245         int err = 0;
 246         struct class_device *class_err;
 247
 248         class_err = class_device_create(msr_class, NULL, MKDEV(MSR_MAJOR, i), NULL, "msr%d",i);
 249         if (IS_ERR(class_err))
 250                 err = PTR_ERR(class_err);
 251         return err;
 252 }
 253
 254 #ifdef CONFIG_HOTPLUG_CPU
 255 static int msr_class_cpu_callback(struct notifier_block *nfb,
 256                                 unsigned long action, void *hcpu)
 257 {
 258         unsigned int cpu = (unsigned long)hcpu;
 259
 260         switch (action) {
 261         case CPU_ONLINE:
 262                 msr_class_device_create(cpu);
 263                 break;
 264         case CPU_DEAD:
 265                 class_device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 266                 break;
 267         }
 268         return NOTIFY_OK;
 269 }
 270
 271 static struct notifier_block __cpuinitdata msr_class_cpu_notifier =
 272 {
 273         .notifier_call = msr_class_cpu_callback,
 274 };
 275 #endif
 276
 277 static int __init msr_init(void)
 278 {
 279         int i, err = 0;
 280         i = 0;
 281
 282         if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
 283                 printk(KERN_ERR "msr: unable to get major %d for msr\n",
 284                        MSR_MAJOR);
 285                 err = -EBUSY;
 286                 goto out;
 287         }
 288         msr_class = class_create(THIS_MODULE, "msr");
 289         if (IS_ERR(msr_class)) {
 290                 err = PTR_ERR(msr_class);
 291                 goto out_chrdev;
 292         }
 293         for_each_online_cpu(i) {
 294                 err = msr_class_device_create(i);
 295                 if (err != 0)
 296                         goto out_class;
 297         }
 298         register_hotcpu_notifier(&msr_class_cpu_notifier);
 299
 300         err = 0;
 301         goto out;
 302
 303 out_class:
 304         i = 0;
 305         for_each_online_cpu(i)
 306                 class_device_destroy(msr_class, MKDEV(MSR_MAJOR, i));
 307         class_destroy(msr_class);
 308 out_chrdev:
 309         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 310 out:
 311         return err;
 312 }
 313
 314 static void __exit msr_exit(void)
 315 {
 316         int cpu = 0;
 317         for_each_online_cpu(cpu)
 318                 class_device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
 319         class_destroy(msr_class);
 320         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 321         unregister_hotcpu_notifier(&msr_class_cpu_notifier);
 322 }
 323
 324 module_init(msr_init);
 325 module_exit(msr_exit)
 326
 327 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 328 MODULE_DESCRIPTION("x86 generic MSR driver");
 329 MODULE_LICENSE("GPL");