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