File: /usr/src/linux/arch/i386/kernel/msr.c
1 #ident "$Id$"
2 /* ----------------------------------------------------------------------- *
3 *
4 * Copyright 2000 H. Peter Anvin - All Rights Reserved
5 *
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.
11 *
12 * ----------------------------------------------------------------------- */
13
14 /*
15 * msr.c
16 *
17 * x86 MSR access device
18 *
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.
22 *
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.
25 */
26
27 #include <linux/module.h>
28 #include <linux/config.h>
29
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>
37
38 #include <asm/processor.h>
39 #include <asm/msr.h>
40 #include <asm/uaccess.h>
41 #include <asm/system.h>
42
43 /* Note: "err" is handled in a funny way below. Otherwise one version
44 of gcc or another breaks. */
45
46 static inline int wrmsr_eio(u32 reg, u32 eax, u32 edx)
47 {
48 int err;
49
50 asm volatile(
51 "1: wrmsr\n"
52 "2:\n"
53 ".section .fixup,\"ax\"\n"
54 "3: movl %4,%0\n"
55 " jmp 2b\n"
56 ".previous\n"
57 ".section __ex_table,\"a\"\n"
58 " .align 4\n"
59 " .long 1b,3b\n"
60 ".previous"
61 : "=&bDS" (err)
62 : "a" (eax), "d" (edx), "c" (reg), "i" (-EIO), "0" (0));
63
64 return err;
65 }
66
67 static inline int rdmsr_eio(u32 reg, u32 *eax, u32 *edx)
68 {
69 int err;
70
71 asm volatile(
72 "1: rdmsr\n"
73 "2:\n"
74 ".section .fixup,\"ax\"\n"
75 "3: movl %4,%0\n"
76 " jmp 2b\n"
77 ".previous\n"
78 ".section __ex_table,\"a\"\n"
79 " .align 4\n"
80 " .long 1b,3b\n"
81 ".previous"
82 : "=&bDS" (err), "=a" (*eax), "=d" (*edx)
83 : "c" (reg), "i" (-EIO), "0" (0));
84
85 return err;
86 }
87
88 #ifdef CONFIG_SMP
89
90 struct msr_command {
91 int cpu;
92 int err;
93 u32 reg;
94 u32 data[2];
95 };
96
97 static void msr_smp_wrmsr(void *cmd_block)
98 {
99 struct msr_command *cmd = (struct msr_command *) cmd_block;
100
101 if ( cmd->cpu == smp_processor_id() )
102 cmd->err = wrmsr_eio(cmd->reg, cmd->data[0], cmd->data[1]);
103 }
104
105 static void msr_smp_rdmsr(void *cmd_block)
106 {
107 struct msr_command *cmd = (struct msr_command *) cmd_block;
108
109 if ( cmd->cpu == smp_processor_id() )
110 cmd->err = rdmsr_eio(cmd->reg, &cmd->data[0], &cmd->data[1]);
111 }
112
113 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
114 {
115 struct msr_command cmd;
116
117 if ( cpu == smp_processor_id() ) {
118 return wrmsr_eio(reg, eax, edx);
119 } else {
120 cmd.cpu = cpu;
121 cmd.reg = reg;
122 cmd.data[0] = eax;
123 cmd.data[1] = edx;
124
125 smp_call_function(msr_smp_wrmsr, &cmd, 1, 1);
126 return cmd.err;
127 }
128 }
129
130 static inline int do_rdmsr(int cpu, u32 reg, u32 *eax, u32 *edx)
131 {
132 struct msr_command cmd;
133
134 if ( cpu == smp_processor_id() ) {
135 return rdmsr_eio(reg, eax, edx);
136 } else {
137 cmd.cpu = cpu;
138 cmd.reg = reg;
139
140 smp_call_function(msr_smp_rdmsr, &cmd, 1, 1);
141
142 *eax = cmd.data[0];
143 *edx = cmd.data[1];
144
145 return cmd.err;
146 }
147 }
148
149 #else /* ! CONFIG_SMP */
150
151 static inline int do_wrmsr(int cpu, u32 reg, u32 eax, u32 edx)
152 {
153 return wrmsr_eio(reg, eax, edx);
154 }
155
156 static inline int do_rdmsr(int cpu, u32 reg, u32 *eax, u32 *edx)
157 {
158 return rdmsr_eio(reg, eax, edx);
159 }
160
161 #endif /* ! CONFIG_SMP */
162
163 static loff_t msr_seek(struct file *file, loff_t offset, int orig)
164 {
165 switch (orig) {
166 case 0:
167 file->f_pos = offset;
168 return file->f_pos;
169 case 1:
170 file->f_pos += offset;
171 return file->f_pos;
172 default:
173 return -EINVAL; /* SEEK_END not supported */
174 }
175 }
176
177 static ssize_t msr_read(struct file * file, char * buf,
178 size_t count, loff_t *ppos)
179 {
180 u32 *tmp = (u32 *)buf;
181 u32 data[2];
182 size_t rv;
183 u32 reg = *ppos;
184 int cpu = MINOR(file->f_dentry->d_inode->i_rdev);
185 int err;
186
187 if ( count % 8 )
188 return -EINVAL; /* Invalid chunk size */
189
190 for ( rv = 0 ; count ; count -= 8 ) {
191 err = do_rdmsr(cpu, reg, &data[0], &data[1]);
192 if ( err )
193 return err;
194 if ( copy_to_user(tmp,&data,8) )
195 return -EFAULT;
196 tmp += 2;
197 }
198
199 return ((char *)tmp) - buf;
200 }
201
202 static ssize_t msr_write(struct file * file, const char * buf,
203 size_t count, loff_t *ppos)
204 {
205 const u32 *tmp = (const u32 *)buf;
206 u32 data[2];
207 size_t rv;
208 u32 reg = *ppos;
209 int cpu = MINOR(file->f_dentry->d_inode->i_rdev);
210 int err;
211
212 if ( count % 8 )
213 return -EINVAL; /* Invalid chunk size */
214
215 for ( rv = 0 ; count ; count -= 8 ) {
216 if ( copy_from_user(&data,tmp,8) )
217 return -EFAULT;
218 err = do_wrmsr(cpu, reg, data[0], data[1]);
219 if ( err )
220 return err;
221 tmp += 2;
222 }
223
224 return ((char *)tmp) - buf;
225 }
226
227 static int msr_open(struct inode *inode, struct file *file)
228 {
229 int cpu = MINOR(file->f_dentry->d_inode->i_rdev);
230 struct cpuinfo_x86 *c = &(cpu_data)[cpu];
231
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 */
236
237 return 0;
238 }
239
240 /*
241 * File operations we support
242 */
243 static struct file_operations msr_fops = {
244 owner: THIS_MODULE,
245 llseek: msr_seek,
246 read: msr_read,
247 write: msr_write,
248 open: msr_open,
249 };
250
251 int __init msr_init(void)
252 {
253 if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
254 printk(KERN_ERR "msr: unable to get major %d for msr\n",
255 MSR_MAJOR);
256 return -EBUSY;
257 }
258
259 return 0;
260 }
261
262 void __exit msr_exit(void)
263 {
264 unregister_chrdev(MSR_MAJOR, "cpu/msr");
265 }
266
267 module_init(msr_init);
268 module_exit(msr_exit)
269
270 EXPORT_NO_SYMBOLS;
271
272 MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
273 MODULE_DESCRIPTION("x86 generic MSR driver");
274