Linux 4.6-rc6
[linux/fpc-iii.git] / arch / x86 / kernel / msr.c
blob7f3550acde1b8ce604f4b5cc8b53c232450c524f
1 /* ----------------------------------------------------------------------- *
3 * Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
4 * Copyright 2009 Intel Corporation; author: H. Peter Anvin
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
9 * USA; either version 2 of the License, or (at your option) any later
10 * version; incorporated herein by reference.
12 * ----------------------------------------------------------------------- */
15 * x86 MSR access device
17 * This device is accessed by lseek() to the appropriate register number
18 * and then read/write in chunks of 8 bytes. A larger size means multiple
19 * reads or writes of the same register.
21 * This driver uses /dev/cpu/%d/msr where %d is the minor number, and on
22 * an SMP box will direct the access to CPU %d.
25 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
27 #include <linux/module.h>
29 #include <linux/types.h>
30 #include <linux/errno.h>
31 #include <linux/fcntl.h>
32 #include <linux/init.h>
33 #include <linux/poll.h>
34 #include <linux/smp.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 #include <linux/uaccess.h>
41 #include <linux/gfp.h>
43 #include <asm/cpufeature.h>
44 #include <asm/msr.h>
46 static struct class *msr_class;
48 static ssize_t msr_read(struct file *file, char __user *buf,
49 size_t count, loff_t *ppos)
51 u32 __user *tmp = (u32 __user *) buf;
52 u32 data[2];
53 u32 reg = *ppos;
54 int cpu = iminor(file_inode(file));
55 int err = 0;
56 ssize_t bytes = 0;
58 if (count % 8)
59 return -EINVAL; /* Invalid chunk size */
61 for (; count; count -= 8) {
62 err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
63 if (err)
64 break;
65 if (copy_to_user(tmp, &data, 8)) {
66 err = -EFAULT;
67 break;
69 tmp += 2;
70 bytes += 8;
73 return bytes ? bytes : err;
76 static ssize_t msr_write(struct file *file, const char __user *buf,
77 size_t count, loff_t *ppos)
79 const u32 __user *tmp = (const u32 __user *)buf;
80 u32 data[2];
81 u32 reg = *ppos;
82 int cpu = iminor(file_inode(file));
83 int err = 0;
84 ssize_t bytes = 0;
86 if (count % 8)
87 return -EINVAL; /* Invalid chunk size */
89 for (; count; count -= 8) {
90 if (copy_from_user(&data, tmp, 8)) {
91 err = -EFAULT;
92 break;
94 err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
95 if (err)
96 break;
97 tmp += 2;
98 bytes += 8;
101 return bytes ? bytes : err;
104 static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
106 u32 __user *uregs = (u32 __user *)arg;
107 u32 regs[8];
108 int cpu = iminor(file_inode(file));
109 int err;
111 switch (ioc) {
112 case X86_IOC_RDMSR_REGS:
113 if (!(file->f_mode & FMODE_READ)) {
114 err = -EBADF;
115 break;
117 if (copy_from_user(&regs, uregs, sizeof regs)) {
118 err = -EFAULT;
119 break;
121 err = rdmsr_safe_regs_on_cpu(cpu, regs);
122 if (err)
123 break;
124 if (copy_to_user(uregs, &regs, sizeof regs))
125 err = -EFAULT;
126 break;
128 case X86_IOC_WRMSR_REGS:
129 if (!(file->f_mode & FMODE_WRITE)) {
130 err = -EBADF;
131 break;
133 if (copy_from_user(&regs, uregs, sizeof regs)) {
134 err = -EFAULT;
135 break;
137 err = wrmsr_safe_regs_on_cpu(cpu, regs);
138 if (err)
139 break;
140 if (copy_to_user(uregs, &regs, sizeof regs))
141 err = -EFAULT;
142 break;
144 default:
145 err = -ENOTTY;
146 break;
149 return err;
152 static int msr_open(struct inode *inode, struct file *file)
154 unsigned int cpu = iminor(file_inode(file));
155 struct cpuinfo_x86 *c;
157 if (!capable(CAP_SYS_RAWIO))
158 return -EPERM;
160 if (cpu >= nr_cpu_ids || !cpu_online(cpu))
161 return -ENXIO; /* No such CPU */
163 c = &cpu_data(cpu);
164 if (!cpu_has(c, X86_FEATURE_MSR))
165 return -EIO; /* MSR not supported */
167 return 0;
171 * File operations we support
173 static const struct file_operations msr_fops = {
174 .owner = THIS_MODULE,
175 .llseek = no_seek_end_llseek,
176 .read = msr_read,
177 .write = msr_write,
178 .open = msr_open,
179 .unlocked_ioctl = msr_ioctl,
180 .compat_ioctl = msr_ioctl,
183 static int msr_device_create(int cpu)
185 struct device *dev;
187 dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu), NULL,
188 "msr%d", cpu);
189 return PTR_ERR_OR_ZERO(dev);
192 static void msr_device_destroy(int cpu)
194 device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
197 static int msr_class_cpu_callback(struct notifier_block *nfb,
198 unsigned long action, void *hcpu)
200 unsigned int cpu = (unsigned long)hcpu;
201 int err = 0;
203 switch (action) {
204 case CPU_UP_PREPARE:
205 err = msr_device_create(cpu);
206 break;
207 case CPU_UP_CANCELED:
208 case CPU_UP_CANCELED_FROZEN:
209 case CPU_DEAD:
210 msr_device_destroy(cpu);
211 break;
213 return notifier_from_errno(err);
216 static struct notifier_block __refdata msr_class_cpu_notifier = {
217 .notifier_call = msr_class_cpu_callback,
220 static char *msr_devnode(struct device *dev, umode_t *mode)
222 return kasprintf(GFP_KERNEL, "cpu/%u/msr", MINOR(dev->devt));
225 static int __init msr_init(void)
227 int i, err = 0;
228 i = 0;
230 if (__register_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr", &msr_fops)) {
231 pr_err("unable to get major %d for msr\n", MSR_MAJOR);
232 err = -EBUSY;
233 goto out;
235 msr_class = class_create(THIS_MODULE, "msr");
236 if (IS_ERR(msr_class)) {
237 err = PTR_ERR(msr_class);
238 goto out_chrdev;
240 msr_class->devnode = msr_devnode;
242 cpu_notifier_register_begin();
243 for_each_online_cpu(i) {
244 err = msr_device_create(i);
245 if (err != 0)
246 goto out_class;
248 __register_hotcpu_notifier(&msr_class_cpu_notifier);
249 cpu_notifier_register_done();
251 err = 0;
252 goto out;
254 out_class:
255 i = 0;
256 for_each_online_cpu(i)
257 msr_device_destroy(i);
258 cpu_notifier_register_done();
259 class_destroy(msr_class);
260 out_chrdev:
261 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
262 out:
263 return err;
266 static void __exit msr_exit(void)
268 int cpu = 0;
270 cpu_notifier_register_begin();
271 for_each_online_cpu(cpu)
272 msr_device_destroy(cpu);
273 class_destroy(msr_class);
274 __unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
275 __unregister_hotcpu_notifier(&msr_class_cpu_notifier);
276 cpu_notifier_register_done();
279 module_init(msr_init);
280 module_exit(msr_exit)
282 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
283 MODULE_DESCRIPTION("x86 generic MSR driver");
284 MODULE_LICENSE("GPL");