| 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 __cpuinit msr_device_create(int cpu) |
| 137 | { |
| 138 | struct device *dev; |
| 139 | |
| 140 | dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), |
| 141 | "msr%d", cpu); |
| 142 | return IS_ERR(dev) ? PTR_ERR(dev) : 0; |
| 143 | } |
| 144 | |
| 145 | static void msr_device_destroy(int cpu) |
| 146 | { |
| 147 | device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu)); |
| 148 | } |
| 149 | |
| 150 | static int __cpuinit msr_class_cpu_callback(struct notifier_block *nfb, |
| 151 | unsigned long action, void *hcpu) |
| 152 | { |
| 153 | unsigned int cpu = (unsigned long)hcpu; |
| 154 | int err = 0; |
| 155 | |
| 156 | switch (action) { |
| 157 | case CPU_UP_PREPARE: |
| 158 | err = msr_device_create(cpu); |
| 159 | break; |
| 160 | case CPU_UP_CANCELED: |
| 161 | case CPU_DEAD: |
| 162 | msr_device_destroy(cpu); |
| 163 | break; |
| 164 | case CPU_UP_CANCELED_FROZEN: |
| 165 | destroy_suspended_device(msr_class, MKDEV(MSR_MAJOR, cpu)); |
| 166 | break; |
| 167 | } |
| 168 | return err ? NOTIFY_BAD : NOTIFY_OK; |
| 169 | } |
| 170 | |
| 171 | static struct notifier_block __cpuinitdata msr_class_cpu_notifier = { |
| 172 | .notifier_call = msr_class_cpu_callback, |
| 173 | }; |
| 174 | |
| 175 | static int __init msr_init(void) |
| 176 | { |
| 177 | int i, err = 0; |
| 178 | i = 0; |
| 179 | |
| 180 | if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) { |
| 181 | printk(KERN_ERR "msr: unable to get major %d for msr\n", |
| 182 | MSR_MAJOR); |
| 183 | err = -EBUSY; |
| 184 | goto out; |
| 185 | } |
| 186 | msr_class = class_create(THIS_MODULE, "msr"); |
| 187 | if (IS_ERR(msr_class)) { |
| 188 | err = PTR_ERR(msr_class); |
| 189 | goto out_chrdev; |
| 190 | } |
| 191 | for_each_online_cpu(i) { |
| 192 | err = msr_device_create(i); |
| 193 | if (err != 0) |
| 194 | goto out_class; |
| 195 | } |
| 196 | register_hotcpu_notifier(&msr_class_cpu_notifier); |
| 197 | |
| 198 | err = 0; |
| 199 | goto out; |
| 200 | |
| 201 | out_class: |
| 202 | i = 0; |
| 203 | for_each_online_cpu(i) |
| 204 | msr_device_destroy(i); |
| 205 | class_destroy(msr_class); |
| 206 | out_chrdev: |
| 207 | unregister_chrdev(MSR_MAJOR, "cpu/msr"); |
| 208 | out: |
| 209 | return err; |
| 210 | } |
| 211 | |
| 212 | static void __exit msr_exit(void) |
| 213 | { |
| 214 | int cpu = 0; |
| 215 | for_each_online_cpu(cpu) |
| 216 | msr_device_destroy(cpu); |
| 217 | class_destroy(msr_class); |
| 218 | unregister_chrdev(MSR_MAJOR, "cpu/msr"); |
| 219 | unregister_hotcpu_notifier(&msr_class_cpu_notifier); |
| 220 | } |
| 221 | |
| 222 | module_init(msr_init); |
| 223 | module_exit(msr_exit) |
| 224 | |
| 225 | MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); |
| 226 | MODULE_DESCRIPTION("x86 generic MSR driver"); |
| 227 | MODULE_LICENSE("GPL"); |