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"); 228