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