3 files changed, 60 insertions, 2 deletions

diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
index dbea4f95fc85..1c058b552e93 100644
--- a/Documentation/ioctl/ioctl-number.txt
+++ b/Documentation/ioctl/ioctl-number.txt
@@ -121,6 +121,7 @@ Code	Seq#	Include File		Comments
 'c'     00-7F   linux/comstats.h        conflict!
 'c'     00-7F   linux/coda.h            conflict!
 'c'     80-9F   arch/s390/include/asm/chsc.h
+'c'     A0-AF   arch/x86/include/asm/msr.h
 'd'     00-FF   linux/char/drm/drm/h    conflict!
 'd'     F0-FF   linux/digi1.h
 'e'     all     linux/digi1.h           conflict!
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 8e56712aa176..7e2b6ba962ff 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -3,10 +3,16 @@
 
 #include <asm/msr-index.h>
 
-#ifdef __KERNEL__
 #ifndef __ASSEMBLY__
 
 #include <linux/types.h>
+#include <linux/ioctl.h>
+
+#define X86_IOC_RDMSR_REGS      _IOWR('c', 0xA0, __u32[8])
+#define X86_IOC_WRMSR_REGS      _IOWR('c', 0xA1, __u32[8])
+
+#ifdef __KERNEL__
+
 #include <asm/asm.h>
 #include <asm/errno.h>
 #include <asm/cpumask.h>
@@ -286,6 +292,6 @@ static inline int wrmsr_safe_regs_on_cpu(unsigned int cpu, u32 regs[8])
         return wrmsr_safe_regs(regs);
 }
 #endif  /* CONFIG_SMP */
-#endif /* __ASSEMBLY__ */
 #endif /* __KERNEL__ */
+#endif /* __ASSEMBLY__ */
 #endif /* _ASM_X86_MSR_H */
diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index 2cfbb4b2c422..7dd950094178 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -1,6 +1,7 @@
 /* ----------------------------------------------------------------------- *
  *
  *   Copyright 2000-2008 H. Peter Anvin - All Rights Reserved
+ *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
  *
  *   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
@@ -121,6 +122,54 @@ static ssize_t msr_write(struct file *file, const char __user *buf,
         return bytes ? bytes : err;
 }
 
+static long msr_ioctl(struct file *file, unsigned int ioc, unsigned long arg)
+{
+        u32 __user *uregs = (u32 __user *)arg;
+        u32 regs[8];
+        int cpu = iminor(file->f_path.dentry->d_inode);
+        int err;
+
+        switch (ioc) {
+        case X86_IOC_RDMSR_REGS:
+                if (!(file->f_mode & FMODE_READ)) {
+                        err = -EBADF;
+                        break;
+                }
+                if (copy_from_user(&regs, uregs, sizeof regs)) {
+                        err = -EFAULT;
+                        break;
+                }
+                err = rdmsr_safe_regs_on_cpu(cpu, regs);
+                if (err)
+                        break;
+                if (copy_to_user(uregs, &regs, sizeof regs))
+                        err = -EFAULT;
+                break;
+
+        case X86_IOC_WRMSR_REGS:
+                if (!(file->f_mode & FMODE_WRITE)) {
+                        err = -EBADF;
+                        break;
+                }
+                if (copy_from_user(&regs, uregs, sizeof regs)) {
+                        err = -EFAULT;
+                        break;
+                }
+                err = wrmsr_safe_regs_on_cpu(cpu, regs);
+                if (err)
+                        break;
+                if (copy_to_user(uregs, &regs, sizeof regs))
+                        err = -EFAULT;
+                break;
+
+        default:
+                err = -ENOTTY;
+                break;
+        }
+
+        return err;
+}
+
 static int msr_open(struct inode *inode, struct file *file)
 {
         unsigned int cpu = iminor(file->f_path.dentry->d_inode);
@@ -151,6 +200,8 @@ static const struct file_operations msr_fops = {
         .read = msr_read,
         .write = msr_write,
         .open = msr_open,
+        .unlocked_ioctl = msr_ioctl,
+        .compat_ioctl = msr_ioctl,
 };
 
 static int __cpuinit msr_device_create(int cpu)