1 /* ----------------------------------------------------------------------- *
3 * Copyright 2000 H. Peter Anvin - All Rights Reserved
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.
11 * ----------------------------------------------------------------------- */
16 * x86 MSR access device
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.
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.
26 #include <linux/module.h>
27 #include <linux/config.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/smp_lock.h>
36 #include <linux/major.h>
39 #include <asm/processor.h>
41 #include <asm/uaccess.h>
42 #include <asm/system.h>
44 /* Note: "err" is handled in a funny way below. Otherwise one version
45 of gcc or another breaks. */
47 static inline int wrmsr_eio(u32 reg, u32 eax, u32 edx)
54 ".section .fixup,\"ax\"\n"
58 ".section __ex_table,\"a\"\n"
63 : "a" (eax), "d" (edx), "c" (reg), "i" (-EIO), "0" (0));
68 static inline int rdmsr_eio(u32 reg, u32 *eax, u32 *edx)
75 ".section .fixup,\"ax\"\n"
79 ".section __ex_table,\"a\"\n"
83 : "=&bDS" (err), "=a" (*eax), "=d" (*edx)
84 : "c" (reg), "i" (-EIO), "0" (0));
98 static void msr_smp_wrmsr(void *cmd_block)
100 struct msr_command *cmd = (struct msr_command *) cmd_block;
102 if ( cmd->cpu == smp_processor_id() )
103 cmd->err = wrmsr_eio(cmd->reg, cmd->data[0], cmd->data[1]);
106 static void msr_smp_rdmsr(void *cmd_block)
108 struct msr_command *cmd = (struct msr_command *) cmd_block;
110 if ( cmd->cpu == smp_processor_id() )
111 cmd->err = rdmsr_eio(cmd->reg, &cmd->data[0], &cmd->data[1]);
114 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
116 struct msr_command cmd;
120 if ( cpu == smp_processor_id() ) {
121 ret = wrmsr_eio(reg, eax, edx);
128 smp_call_function(msr_smp_wrmsr, &cmd, 1, 1);
135 static inline int do_rdmsr(int cpu, u32 reg, u32 *eax, u32 *edx)
137 struct msr_command cmd;
141 if ( cpu == smp_processor_id() ) {
142 ret = rdmsr_eio(reg, eax, edx);
147 smp_call_function(msr_smp_rdmsr, &cmd, 1, 1);
158 #else /* ! CONFIG_SMP */
160 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
162 return wrmsr_eio(reg, eax, edx);
165 static inline int do_rdmsr(int cpu, u32 reg, u32 *eax, u32 *edx)
167 return rdmsr_eio(reg, eax, edx);
170 #endif /* ! CONFIG_SMP */
172 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
174 loff_t ret = -EINVAL;
178 file->f_pos = offset;
182 file->f_pos += offset;
189 static ssize_t msr_read(struct file * file, char __user * buf,
190 size_t count, loff_t *ppos)
192 char __user *tmp = buf;
196 int cpu = iminor(file->f_dentry->d_inode);
200 return -EINVAL; /* Invalid chunk size */
202 for ( rv = 0 ; count ; count -= 8 ) {
203 err = do_rdmsr(cpu, reg, &data[0], &data[1]);
206 if ( copy_to_user(tmp,&data,8) )
214 static ssize_t msr_write(struct file * file, const char __user * buf,
215 size_t count, loff_t *ppos)
217 const char __user *tmp = buf;
221 int cpu = iminor(file->f_dentry->d_inode);
225 return -EINVAL; /* Invalid chunk size */
227 for ( rv = 0 ; count ; count -= 8 ) {
228 if ( copy_from_user(&data,tmp,8) )
230 err = do_wrmsr(cpu, reg, data[0], data[1]);
239 static int msr_open(struct inode *inode, struct file *file)
241 int cpu = iminor(file->f_dentry->d_inode);
242 struct cpuinfo_x86 *c = &(cpu_data)[cpu];
244 if (cpu >= NR_CPUS || !cpu_online(cpu))
245 return -ENXIO; /* No such CPU */
246 if ( !cpu_has(c, X86_FEATURE_MSR) )
247 return -EIO; /* MSR not supported */
253 * File operations we support
255 static struct file_operations msr_fops = {
256 .owner = THIS_MODULE,
263 int __init msr_init(void)
265 if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
266 printk(KERN_ERR "msr: unable to get major %d for msr\n",
274 void __exit msr_exit(void)
276 unregister_chrdev(MSR_MAJOR, "cpu/msr");
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");