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
msr_seek(struct file * file,loff_t offset,int orig)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
msr_read(struct file * file,char __user * buf,size_t count,loff_t * ppos)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
msr_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)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
msr_open(struct inode * inode,struct file * file)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
msr_device_create(int cpu)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
msr_device_destroy(int cpu)171 static void msr_device_destroy(int cpu)
172 {
173 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
174 }
175
msr_class_cpu_callback(struct notifier_block * nfb,unsigned long action,void * hcpu)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
msr_init(void)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
msr_exit(void)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