2 /* ----------------------------------------------------------------------- *
4 * Copyright 2000 H. Peter Anvin - All Rights Reserved
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 * ----------------------------------------------------------------------- */
17 * x86 MSR access device
19 * This device is accessed by lseek() to the appropriate register number
20 * and then read/write in chunks of 8 bytes. A larger size means multiple
21 * reads or writes of the same register.
23 * This driver uses /dev/cpu/%d/msr where %d is the minor number, and on
24 * an SMP box will direct the access to CPU %d.
27 #include <linux/module.h>
28 #include <linux/config.h>
30 #include <linux/types.h>
31 #include <linux/errno.h>
32 #include <linux/fcntl.h>
33 #include <linux/init.h>
34 #include <linux/poll.h>
35 #include <linux/smp.h>
36 #include <linux/major.h>
38 #include <asm/processor.h>
40 #include <asm/uaccess.h>
41 #include <asm/system.h>
43 /* Note: "err" is handled in a funny way below. Otherwise one version
44 of gcc or another breaks. */
46 static inline int wrmsr_eio(u32 reg, u32 eax, u32 edx)
53 ".section .fixup,\"ax\"\n"
57 ".section __ex_table,\"a\"\n"
62 : "a" (eax), "d" (edx), "c" (reg), "i" (-EIO), "0" (0));
67 static inline int rdmsr_eio(u32 reg, u32 *eax, u32 *edx)
74 ".section .fixup,\"ax\"\n"
78 ".section __ex_table,\"a\"\n"
82 : "=&bDS" (err), "=a" (*eax), "=d" (*edx)
83 : "c" (reg), "i" (-EIO), "0" (0));
97 static void msr_smp_wrmsr(void *cmd_block)
99 struct msr_command *cmd = (struct msr_command *) cmd_block;
101 if ( cmd->cpu == smp_processor_id() )
102 cmd->err = wrmsr_eio(cmd->reg, cmd->data[0], cmd->data[1]);
105 static void msr_smp_rdmsr(void *cmd_block)
107 struct msr_command *cmd = (struct msr_command *) cmd_block;
109 if ( cmd->cpu == smp_processor_id() )
110 cmd->err = rdmsr_eio(cmd->reg, &cmd->data[0], &cmd->data[1]);
113 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
115 struct msr_command cmd;
117 if ( cpu == smp_processor_id() ) {
118 return wrmsr_eio(reg, eax, edx);
125 smp_call_function(msr_smp_wrmsr, &cmd, 1, 1);
130 static inline int do_rdmsr(int cpu, u32 reg, u32 *eax, u32 *edx)
132 struct msr_command cmd;
134 if ( cpu == smp_processor_id() ) {
135 return rdmsr_eio(reg, eax, edx);
140 smp_call_function(msr_smp_rdmsr, &cmd, 1, 1);
149 #else /* ! CONFIG_SMP */
151 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
153 return wrmsr_eio(reg, eax, edx);
156 static inline int do_rdmsr(int cpu, u32 reg, u32 *eax, u32 *edx)
158 return rdmsr_eio(reg, eax, edx);
161 #endif /* ! CONFIG_SMP */
163 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
167 file->f_pos = offset;
170 file->f_pos += offset;
173 return -EINVAL; /* SEEK_END not supported */
177 static ssize_t msr_read(struct file * file, char * buf,
178 size_t count, loff_t *ppos)
180 u32 *tmp = (u32 *)buf;
184 int cpu = MINOR(file->f_dentry->d_inode->i_rdev);
188 return -EINVAL; /* Invalid chunk size */
190 for ( rv = 0 ; count ; count -= 8 ) {
191 err = do_rdmsr(cpu, reg, &data[0], &data[1]);
194 if ( copy_to_user(tmp,&data,8) )
199 return ((char *)tmp) - buf;
202 static ssize_t msr_write(struct file * file, const char * buf,
203 size_t count, loff_t *ppos)
205 const u32 *tmp = (const u32 *)buf;
209 int cpu = MINOR(file->f_dentry->d_inode->i_rdev);
213 return -EINVAL; /* Invalid chunk size */
215 for ( rv = 0 ; count ; count -= 8 ) {
216 if ( copy_from_user(&data,tmp,8) )
218 err = do_wrmsr(cpu, reg, data[0], data[1]);
224 return ((char *)tmp) - buf;
227 static int msr_open(struct inode *inode, struct file *file)
229 int cpu = MINOR(file->f_dentry->d_inode->i_rdev);
230 struct cpuinfo_x86 *c = &(cpu_data)[cpu];
232 if ( !(cpu_online_map & (1UL << cpu)) )
233 return -ENXIO; /* No such CPU */
234 if ( !test_bit(X86_FEATURE_MSR, &c->x86_capability) )
235 return -EIO; /* MSR not supported */
241 * File operations we support
243 static struct file_operations msr_fops = {
251 int __init msr_init(void)
253 if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
254 printk(KERN_ERR "msr: unable to get major %d for msr\n",
262 void __exit msr_exit(void)
264 unregister_chrdev(MSR_MAJOR, "cpu/msr");
267 module_init(msr_init);
268 module_exit(msr_exit)
272 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
273 MODULE_DESCRIPTION("x86 generic MSR driver");
274 MODULE_LICENSE("GPL");