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/* ----------------------------------------------------------------------- *
*
* Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, Inc., 675 Mass Ave, Cambridge MA 02139,
* USA; either version 2 of the License, or (at your option) any later
* version; incorporated herein by reference.
*
* ----------------------------------------------------------------------- */
/*
* x86 MSR access device
*
* This device is accessed by lseek() to the appropriate register number
* and then read/write in chunks of 8 bytes. A larger size means multiple
* reads or writes of the same register.
*
* This driver uses /dev/cpu/%d/msr where %d is the minor number, and on
* an SMP box will direct the access to CPU %d.
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/fcntl.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/major.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
#include <asm/processor.h>
#include <asm/msr.h>
#include <asm/uaccess.h>
#include <asm/system.h>
static struct class *msr_class;
static loff_t msr_seek(struct file *file, loff_t offset, int orig)
{
loff_t ret;
struct inode *inode = file->f_mapping->host;
mutex_lock(&inode->i_mutex);
switch (orig) {
case 0:
file->f_pos = offset;
ret = file->f_pos;
break;
case 1:
file->f_pos += offset;
ret = file->f_pos;
break;
default:
ret = -EINVAL;
}
mutex_unlock(&inode->i_mutex);
return ret;
}
static ssize_t msr_read(struct file *file, char __user *buf,
size_t count, loff_t *ppos)
{
u32 __user *tmp = (u32 __user *) buf;
u32 data[2];
u32 reg = *ppos;
int cpu = iminor(file->f_path.dentry->d_inode);
int err;
if (count % 8)
return -EINVAL; /* Invalid chunk size */
for (; count; count -= 8) {
err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
if (err)
return -EIO;
if (copy_to_user(tmp, &data, 8))
return -EFAULT;
tmp += 2;
}
return ((char __user *)tmp) - buf;
}
static ssize_t msr_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
const u32 __user *tmp = (const u32 __user *)buf;
u32 data[2];
u32 reg = *ppos;
int cpu = iminor(file->f_path.dentry->d_inode);
int err;
if (count % 8)
return -EINVAL; /* Invalid chunk size */
for (; count; count -= 8) {
if (copy_from_user(&data, tmp, 8))
return -EFAULT;
err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]);
if (err)
return -EIO;
tmp += 2;
}
return ((char __user *)tmp) - buf;
}
static int msr_open(struct inode *inode, struct file *file)
{
unsigned int cpu = iminor(file->f_path.dentry->d_inode);
struct cpuinfo_x86 *c = &cpu_data(cpu);
if (cpu >= NR_CPUS || !cpu_online(cpu))
return -ENXIO; /* No such CPU */
if (!cpu_has(c, X86_FEATURE_MSR))
return -EIO; /* MSR not supported */
return 0;
}
/*
* File operations we support
*/
static const struct file_operations msr_fops = {
.owner = THIS_MODULE,
.llseek = msr_seek,
.read = msr_read,
.write = msr_write,
.open = msr_open,
};
static int __cpuinit msr_device_create(int cpu)
{
struct device *dev;
dev = device_create(msr_class, NULL, MKDEV(MSR_MAJOR, cpu),
"msr%d", cpu);
return IS_ERR(dev) ? PTR_ERR(dev) : 0;
}
static void msr_device_destroy(int cpu)
{
device_destroy(msr_class, MKDEV(MSR_MAJOR, cpu));
}
static int __cpuinit msr_class_cpu_callback(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
unsigned int cpu = (unsigned long)hcpu;
int err = 0;
switch (action) {
case CPU_UP_PREPARE:
err = msr_device_create(cpu);
break;
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
case CPU_DEAD:
msr_device_destroy(cpu);
break;
}
return err ? NOTIFY_BAD : NOTIFY_OK;
}
static struct notifier_block __refdata msr_class_cpu_notifier = {
.notifier_call = msr_class_cpu_callback,
};
static int __init msr_init(void)
{
int i, err = 0;
i = 0;
if (register_chrdev(MSR_MAJOR, "cpu/msr", &msr_fops)) {
printk(KERN_ERR "msr: unable to get major %d for msr\n",
MSR_MAJOR);
err = -EBUSY;
goto out;
}
msr_class = class_create(THIS_MODULE, "msr");
if (IS_ERR(msr_class)) {
err = PTR_ERR(msr_class);
goto out_chrdev;
}
for_each_online_cpu(i) {
err = msr_device_create(i);
if (err != 0)
goto out_class;
}
register_hotcpu_notifier(&msr_class_cpu_notifier);
err = 0;
goto out;
out_class:
i = 0;
for_each_online_cpu(i)
msr_device_destroy(i);
class_destroy(msr_class);
out_chrdev:
unregister_chrdev(MSR_MAJOR, "cpu/msr");
out:
return err;
}
static void __exit msr_exit(void)
{
int cpu = 0;
for_each_online_cpu(cpu)
msr_device_destroy(cpu);
class_destroy(msr_class);
unregister_chrdev(MSR_MAJOR, "cpu/msr");
unregister_hotcpu_notifier(&msr_class_cpu_notifier);
}
module_init(msr_init);
module_exit(msr_exit)
MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>");
MODULE_DESCRIPTION("x86 generic MSR driver");
MODULE_LICENSE("GPL");
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