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 * msr.c 15 * 16 * x86 MSR access device 17 * 18 * This device is accessed by lseek() to the appropriate register number 19 * and then read/write in chunks of 8 bytes. A larger size means multiple 20 * reads or writes of the same register. 21 * 22 * This driver uses /dev/cpu/%d/msr where %d is the minor number, and on 23 * an SMP box will direct the access to CPU %d. 24 */ 25 26 #include <linux/module.h> 27 28 #include <linux/types.h> 29 #include <linux/errno.h> 30 #include <linux/fcntl.h> 31 #include <linux/init.h> 32 #include <linux/poll.h> 33 #include <linux/smp.h> 34 #include <linux/smp_lock.h> 35 #include <linux/major.h> 36 #include <linux/fs.h> 37 #include <linux/device.h> 38 #include <linux/cpu.h> 39 #include <linux/notifier.h> 40 41 #include <asm/processor.h> 42 #include <asm/msr.h> 43 #include <asm/uaccess.h> 44 #include <asm/system.h> 45 46 static struct class *msr_class; 47 48 static loff_t msr_seek(struct file *file, loff_t offset, int orig) 49 { 50 loff_t ret = -EINVAL; 51 52 lock_kernel(); 53 switch (orig) { 54 case 0: 55 file->f_pos = offset; 56 ret = file->f_pos; 57 break; 58 case 1: 59 file->f_pos += offset; 60 ret = file->f_pos; 61 } 62 unlock_kernel(); 63 return ret; 64 } 65 66 static ssize_t msr_read(struct file *file, char __user * buf, 67 size_t count, loff_t * ppos) 68 { 69 u32 __user *tmp = (u32 __user *) buf; 70 u32 data[2]; 71 u32 reg = *ppos; 72 int cpu = iminor(file->f_path.dentry->d_inode); 73 int err; 74 75 if (count % 8) 76 return -EINVAL; /* Invalid chunk size */ 77 78 for (; count; count -= 8) { 79 err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]); 80 if (err) 81 return -EIO; 82 if (copy_to_user(tmp, &data, 8)) 83 return -EFAULT; 84 tmp += 2; 85 } 86 87 return ((char __user *)tmp) - buf; 88 } 89 90 static ssize_t msr_write(struct file *file, const char __user *buf, 91 size_t count, loff_t *ppos) 92 { 93 const u32 __user *tmp = (const u32 __user *)buf; 94 u32 data[2]; 95 u32 reg = *ppos; 96 int cpu = iminor(file->f_path.dentry->d_inode); 97 int err; 98 99 if (count % 8) 100 return -EINVAL; /* Invalid chunk size */ 101 102 for (; count; count -= 8) { 103 if (copy_from_user(&data, tmp, 8)) 104 return -EFAULT; 105 err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]); 106 if (err) 107 return -EIO; 108 tmp += 2; 109 } 110 111 return ((char __user *)tmp) - buf; 112 } 113 114 static int msr_open(struct inode *inode, struct file *file) 115 { 116 unsigned int cpu = iminor(file->f_path.dentry->d_inode); 117 struct cpuinfo_x86 *c = &(cpu_data)[cpu]; 118 119 if (cpu >= NR_CPUS || !cpu_online(cpu)) 120 return -ENXIO; /* No such CPU */ 121 if (!cpu_has(c, X86_FEATURE_MSR)) 122 return -EIO; /* MSR not supported */ 123 124 return 0; 125 } 126 127 /* 128 * File operations we support 129 */ 130 static const struct file_operations msr_fops = { 131 .owner = THIS_MODULE, 132 .llseek = msr_seek, 133 .read = msr_read, 134 .write = msr_write, 135 .open = msr_open, 136 }; 137 138 static int msr_device_create(int i) 139 { 140 int err = 0; 141 struct device *dev; 142 143 dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, i), "msr%d",i); 144 if (IS_ERR(dev)) 145 err = PTR_ERR(dev); 146 return err; 147 } 148 149 static int msr_class_cpu_callback(struct notifier_block *nfb, 150 unsigned long action, void *hcpu) 151 { 152 unsigned int cpu = (unsigned long)hcpu; 153 154 switch (action) { 155 case CPU_ONLINE: 156 case CPU_ONLINE_FROZEN: 157 msr_device_create(cpu); 158 break; 159 case CPU_DEAD: 160 case CPU_DEAD_FROZEN: 161 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu)); 162 break; 163 } 164 return NOTIFY_OK; 165 } 166 167 static struct notifier_block __cpuinitdata msr_class_cpu_notifier = 168 { 169 .notifier_call = msr_class_cpu_callback, 170 }; 171 172 static int __init msr_init(void) 173 { 174 int i, err = 0; 175 i = 0; 176 177 if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) { 178 printk(KERN_ERR "msr: unable to get major %d for msr\n", 179 MSR_MAJOR); 180 err = -EBUSY; 181 goto out; 182 } 183 msr_class = class_create(THIS_MODULE, "msr"); 184 if (IS_ERR(msr_class)) { 185 err = PTR_ERR(msr_class); 186 goto out_chrdev; 187 } 188 for_each_online_cpu(i) { 189 err = msr_device_create(i); 190 if (err != 0) 191 goto out_class; 192 } 193 register_hotcpu_notifier(&msr_class_cpu_notifier); 194 195 err = 0; 196 goto out; 197 198 out_class: 199 i = 0; 200 for_each_online_cpu(i) 201 device_destroy(msr_class, MKDEV(MSR_MAJOR, i)); 202 class_destroy(msr_class); 203 out_chrdev: 204 unregister_chrdev(MSR_MAJOR, "cpu/msr"); 205 out: 206 return err; 207 } 208 209 static void __exit msr_exit(void) 210 { 211 int cpu = 0; 212 for_each_online_cpu(cpu) 213 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu)); 214 class_destroy(msr_class); 215 unregister_chrdev(MSR_MAJOR, "cpu/msr"); 216 unregister_hotcpu_notifier(&msr_class_cpu_notifier); 217 } 218 219 module_init(msr_init); 220 module_exit(msr_exit) 221 222 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); 223 MODULE_DESCRIPTION("x86 generic MSR driver"); 224 MODULE_LICENSE("GPL"); 225