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_simple *msr_class;
  48
  49 /* Note: "err" is handled in a funny way below.  Otherwise one version
  50    of gcc or another breaks. */
  51
  52 static inline int wrmsr_eio(u32 reg, u32 eax, u32 edx)
  53 {
  54         int err;
  55
  56         asm volatile ("1:       wrmsr\n"
  57                       "2:\n"
  58                       ".section .fixup,\"ax\"\n"
  59                       "3:       movl %4,%0\n"
  60                       " jmp 2b\n"
  61                       ".previous\n"
  62                       ".section __ex_table,\"a\"\n"
  63                       " .align 4\n" "   .long 1b,3b\n" ".previous":"=&bDS" (err)
  64                       :"a"(eax), "d"(edx), "c"(reg), "i"(-EIO), "0"(0));
  65
  66         return err;
  67 }
  68
  69 static inline int rdmsr_eio(u32 reg, u32 *eax, u32 *edx)
  70 {
  71         int err;
  72
  73         asm volatile ("1:       rdmsr\n"
  74                       "2:\n"
  75                       ".section .fixup,\"ax\"\n"
  76                       "3:       movl %4,%0\n"
  77                       " jmp 2b\n"
  78                       ".previous\n"
  79                       ".section __ex_table,\"a\"\n"
  80                       " .align 4\n"
  81                       " .long 1b,3b\n"
  82                       ".previous":"=&bDS" (err), "=a"(*eax), "=d"(*edx)
  83                       :"c"(reg), "i"(-EIO), "0"(0));
  84
  85         return err;
  86 }
  87
  88 #ifdef CONFIG_SMP
  89
  90 struct msr_command {
  91         int cpu;
  92         int err;
  93         u32 reg;
  94         u32 data[2];
  95 };
  96
  97 static void msr_smp_wrmsr(void *cmd_block)
  98 {
  99         struct msr_command *cmd = (struct msr_command *)cmd_block;
 100
 101         if (cmd->cpu == smp_processor_id())
 102                 cmd->err = wrmsr_eio(cmd->reg, cmd->data[0], cmd->data[1]);
 103 }
 104
 105 static void msr_smp_rdmsr(void *cmd_block)
 106 {
 107         struct msr_command *cmd = (struct msr_command *)cmd_block;
 108
 109         if (cmd->cpu == smp_processor_id())
 110                 cmd->err = rdmsr_eio(cmd->reg, &cmd->data[0], &cmd->data[1]);
 111 }
 112
 113 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
 114 {
 115         struct msr_command cmd;
 116         int ret;
 117
 118         preempt_disable();
 119         if (cpu == smp_processor_id()) {
 120                 ret = wrmsr_eio(reg, eax, edx);
 121         } else {
 122                 cmd.cpu = cpu;
 123                 cmd.reg = reg;
 124                 cmd.data[0] = eax;
 125                 cmd.data[1] = edx;
 126
 127                 smp_call_function(msr_smp_wrmsr, &cmd, 1, 1);
 128                 ret = cmd.err;
 129         }
 130         preempt_enable();
 131         return ret;
 132 }
 133
 134 static inline int do_rdmsr(int cpu, u32 reg, u32 * eax, u32 * edx)
 135 {
 136         struct msr_command cmd;
 137         int ret;
 138
 139         preempt_disable();
 140         if (cpu == smp_processor_id()) {
 141                 ret = rdmsr_eio(reg, eax, edx);
 142         } else {
 143                 cmd.cpu = cpu;
 144                 cmd.reg = reg;
 145
 146                 smp_call_function(msr_smp_rdmsr, &cmd, 1, 1);
 147
 148                 *eax = cmd.data[0];
 149                 *edx = cmd.data[1];
 150
 151                 ret = cmd.err;
 152         }
 153         preempt_enable();
 154         return ret;
 155 }
 156
 157 #else                           /* ! CONFIG_SMP */
 158
 159 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
 160 {
 161         return wrmsr_eio(reg, eax, edx);
 162 }
 163
 164 static inline int do_rdmsr(int cpu, u32 reg, u32 *eax, u32 *edx)
 165 {
 166         return rdmsr_eio(reg, eax, edx);
 167 }
 168
 169 #endif                          /* ! CONFIG_SMP */
 170
 171 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
 172 {
 173         loff_t ret = -EINVAL;
 174
 175         lock_kernel();
 176         switch (orig) {
 177         case 0:
 178                 file->f_pos = offset;
 179                 ret = file->f_pos;
 180                 break;
 181         case 1:
 182                 file->f_pos += offset;
 183                 ret = file->f_pos;
 184         }
 185         unlock_kernel();
 186         return ret;
 187 }
 188
 189 static ssize_t msr_read(struct file *file, char __user * buf,
 190                         size_t count, loff_t * ppos)
 191 {
 192         u32 __user *tmp = (u32 __user *) buf;
 193         u32 data[2];
 194         size_t rv;
 195         u32 reg = *ppos;
 196         int cpu = iminor(file->f_dentry->d_inode);
 197         int err;
 198
 199         if (count % 8)
 200                 return -EINVAL; /* Invalid chunk size */
 201
 202         for (rv = 0; count; count -= 8) {
 203                 err = do_rdmsr(cpu, reg, &data[0], &data[1]);
 204                 if (err)
 205                         return err;
 206                 if (copy_to_user(tmp, &data, 8))
 207                         return -EFAULT;
 208                 tmp += 2;
 209         }
 210
 211         return ((char __user *)tmp) - buf;
 212 }
 213
 214 static ssize_t msr_write(struct file *file, const char __user *buf,
 215                          size_t count, loff_t *ppos)
 216 {
 217         const u32 __user *tmp = (const u32 __user *)buf;
 218         u32 data[2];
 219         size_t rv;
 220         u32 reg = *ppos;
 221         int cpu = iminor(file->f_dentry->d_inode);
 222         int err;
 223
 224         if (count % 8)
 225                 return -EINVAL; /* Invalid chunk size */
 226
 227         for (rv = 0; count; count -= 8) {
 228                 if (copy_from_user(&data, tmp, 8))
 229                         return -EFAULT;
 230                 err = do_wrmsr(cpu, reg, data[0], data[1]);
 231                 if (err)
 232                         return err;
 233                 tmp += 2;
 234         }
 235
 236         return ((char __user *)tmp) - buf;
 237 }
 238
 239 static int msr_open(struct inode *inode, struct file *file)
 240 {
 241         unsigned int cpu = iminor(file->f_dentry->d_inode);
 242         struct cpuinfo_x86 *c = &(cpu_data)[cpu];
 243
 244         if (cpu >= NR_CPUS || !cpu_online(cpu))
 245                 return -ENXIO;  /* No such CPU */
 246         if (!cpu_has(c, X86_FEATURE_MSR))
 247                 return -EIO;    /* MSR not supported */
 248
 249         return 0;
 250 }
 251
 252 /*
 253  * File operations we support
 254  */
 255 static struct file_operations msr_fops = {
 256         .owner = THIS_MODULE,
 257         .llseek = msr_seek,
 258         .read = msr_read,
 259         .write = msr_write,
 260         .open = msr_open,
 261 };
 262
 263 static int msr_class_simple_device_add(int i)
 264 {
 265         int err = 0;
 266         struct class_device *class_err;
 267
 268         class_err = class_simple_device_add(msr_class, MKDEV(MSR_MAJOR, i), NULL, "msr%d",i);
 269         if (IS_ERR(class_err))
 270                 err = PTR_ERR(class_err);
 271         return err;
 272 }
 273
 274 static int __devinit msr_class_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
 275 {
 276         unsigned int cpu = (unsigned long)hcpu;
 277
 278         switch (action) {
 279         case CPU_ONLINE:
 280                 msr_class_simple_device_add(cpu);
 281                 break;
 282         case CPU_DEAD:
 283                 class_simple_device_remove(MKDEV(MSR_MAJOR, cpu));
 284                 break;
 285         }
 286         return NOTIFY_OK;
 287 }
 288
 289 static struct notifier_block msr_class_cpu_notifier =
 290 {
 291         .notifier_call = msr_class_cpu_callback,
 292 };
 293
 294 static int __init msr_init(void)
 295 {
 296         int i, err = 0;
 297         i = 0;
 298
 299         if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
 300                 printk(KERN_ERR "msr: unable to get major %d for msr\n",
 301                        MSR_MAJOR);
 302                 err = -EBUSY;
 303                 goto out;
 304         }
 305         msr_class = class_simple_create(THIS_MODULE, "msr");
 306         if (IS_ERR(msr_class)) {
 307                 err = PTR_ERR(msr_class);
 308                 goto out_chrdev;
 309         }
 310         for_each_online_cpu(i) {
 311                 err = msr_class_simple_device_add(i);
 312                 if (err != 0)
 313                         goto out_class;
 314         }
 315         register_cpu_notifier(&msr_class_cpu_notifier);
 316
 317         err = 0;
 318         goto out;
 319
 320 out_class:
 321         i = 0;
 322         for_each_online_cpu(i)
 323                 class_simple_device_remove(MKDEV(MSR_MAJOR, i));
 324         class_simple_destroy(msr_class);
 325 out_chrdev:
 326         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 327 out:
 328         return err;
 329 }
 330
 331 static void __exit msr_exit(void)
 332 {
 333         int cpu = 0;
 334         for_each_online_cpu(cpu)
 335                 class_simple_device_remove(MKDEV(MSR_MAJOR, cpu));
 336         class_simple_destroy(msr_class);
 337         unregister_chrdev(MSR_MAJOR, "cpu/msr");
 338         unregister_cpu_notifier(&msr_class_cpu_notifier);
 339 }
 340
 341 module_init(msr_init);
 342 module_exit(msr_exit)
 343
 344 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
 345 MODULE_DESCRIPTION("x86 generic MSR driver");
 346 MODULE_LICENSE("GPL");