1 /* ----------------------------------------------------------------------- * 2 * 3 * Copyright 2000-2008 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; 49 struct inode *inode = file->f_mapping->host; 50 51 mutex_lock(&inode->i_mutex); 52 switch (orig) { 53 case 0: 54 file->f_pos = offset; 55 ret = file->f_pos; 56 break; 57 case 1: 58 file->f_pos += offset; 59 ret = file->f_pos; 60 break; 61 default: 62 ret = -EINVAL; 63 } 64 mutex_unlock(&inode->i_mutex); 65 return ret; 66 } 67 68 static ssize_t msr_read(struct file *file, char __user *buf, 69 size_t count, loff_t *ppos) 70 { 71 u32 __user *tmp = (u32 __user *) buf; 72 u32 data[2]; 73 u32 reg = *ppos; 74 int cpu = iminor(file->f_path.dentry->d_inode); 75 int err = 0; 76 ssize_t bytes = 0; 77 78 if (count % 8) 79 return -EINVAL; /* Invalid chunk size */ 80 81 for (; count; count -= 8) { 82 err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]); 83 if (err) { 84 if (err == -EFAULT) /* Fix idiotic error code */ 85 err = -EIO; 86 break; 87 } 88 if (copy_to_user(tmp, &data, 8)) { 89 err = -EFAULT; 90 break; 91 } 92 tmp += 2; 93 bytes += 8; 94 } 95 96 return bytes ? bytes : err; 97 } 98 99 static ssize_t msr_write(struct file *file, const char __user *buf, 100 size_t count, loff_t *ppos) 101 { 102 const u32 __user *tmp = (const u32 __user *)buf; 103 u32 data[2]; 104 u32 reg = *ppos; 105 int cpu = iminor(file->f_path.dentry->d_inode); 106 int err = 0; 107 ssize_t bytes = 0; 108 109 if (count % 8) 110 return -EINVAL; /* Invalid chunk size */ 111 112 for (; count; count -= 8) { 113 if (copy_from_user(&data, tmp, 8)) { 114 err = -EFAULT; 115 break; 116 } 117 err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]); 118 if (err) { 119 if (err == -EFAULT) /* Fix idiotic error code */ 120 err = -EIO; 121 break; 122 } 123 tmp += 2; 124 bytes += 8; 125 } 126 127 return bytes ? bytes : err; 128 } 129 130 static int msr_open(struct inode *inode, struct file *file) 131 { 132 unsigned int cpu = iminor(file->f_path.dentry->d_inode); 133 struct cpuinfo_x86 *c = &cpu_data(cpu); 134 int ret = 0; 135 136 lock_kernel(); 137 cpu = iminor(file->f_path.dentry->d_inode); 138 139 if (cpu >= nr_cpu_ids || !cpu_online(cpu)) { 140 ret = -ENXIO; /* No such CPU */ 141 goto out; 142 } 143 c = &cpu_data(cpu); 144 if (!cpu_has(c, X86_FEATURE_MSR)) 145 ret = -EIO; /* MSR not supported */ 146 out: 147 unlock_kernel(); 148 return ret; 149 } 150 151 /* 152 * File operations we support 153 */ 154 static const struct file_operations msr_fops = { 155 .owner = THIS_MODULE, 156 .llseek = msr_seek, 157 .read = msr_read, 158 .write = msr_write, 159 .open = msr_open, 160 }; 161 162 static int __cpuinit msr_device_create(int cpu) 163 { 164 struct device *dev; 165 166 dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL, 167 "msr%d", cpu); 168 return IS_ERR(dev) ? PTR_ERR(dev) : 0; 169 } 170 171 static void msr_device_destroy(int cpu) 172 { 173 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu)); 174 } 175 176 static int __cpuinit msr_class_cpu_callback(struct notifier_block *nfb, 177 unsigned long action, void *hcpu) 178 { 179 unsigned int cpu = (unsigned long)hcpu; 180 int err = 0; 181 182 switch (action) { 183 case CPU_UP_PREPARE: 184 err = msr_device_create(cpu); 185 break; 186 case CPU_UP_CANCELED: 187 case CPU_UP_CANCELED_FROZEN: 188 case CPU_DEAD: 189 msr_device_destroy(cpu); 190 break; 191 } 192 return err ? NOTIFY_BAD : NOTIFY_OK; 193 } 194 195 static struct notifier_block __refdata msr_class_cpu_notifier = { 196 .notifier_call = msr_class_cpu_callback, 197 }; 198 199 static int __init msr_init(void) 200 { 201 int i, err = 0; 202 i = 0; 203 204 if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) { 205 printk(KERN_ERR "msr: unable to get major %d for msr\n", 206 MSR_MAJOR); 207 err = -EBUSY; 208 goto out; 209 } 210 msr_class = class_create(THIS_MODULE, "msr"); 211 if (IS_ERR(msr_class)) { 212 err = PTR_ERR(msr_class); 213 goto out_chrdev; 214 } 215 for_each_online_cpu(i) { 216 err = msr_device_create(i); 217 if (err != 0) 218 goto out_class; 219 } 220 register_hotcpu_notifier(&msr_class_cpu_notifier); 221 222 err = 0; 223 goto out; 224 225 out_class: 226 i = 0; 227 for_each_online_cpu(i) 228 msr_device_destroy(i); 229 class_destroy(msr_class); 230 out_chrdev: 231 unregister_chrdev(MSR_MAJOR, "cpu/msr"); 232 out: 233 return err; 234 } 235 236 static void __exit msr_exit(void) 237 { 238 int cpu = 0; 239 for_each_online_cpu(cpu) 240 msr_device_destroy(cpu); 241 class_destroy(msr_class); 242 unregister_chrdev(MSR_MAJOR, "cpu/msr"); 243 unregister_hotcpu_notifier(&msr_class_cpu_notifier); 244 } 245 246 module_init(msr_init); 247 module_exit(msr_exit) 248 249 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); 250 MODULE_DESCRIPTION("x86 generic MSR driver"); 251 MODULE_LICENSE("GPL"); 252