Add ioctl to msr driver to trigger int18

This is useful to inject machine checks on AMD CPUs.

I could have written an own driver, but it seemed overkill.
Signed-off-by: Andi Kleen <ak@suse.de>

---
 arch/x86/kernel/msr.c |   20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

Index: linux/arch/x86/kernel/msr.c
===================================================================
--- linux.orig/arch/x86/kernel/msr.c
+++ linux/arch/x86/kernel/msr.c
@@ -122,6 +122,24 @@ static int msr_open(struct inode *inode,
 	return 0;
 }
 
+#define MSR_INJECT_INT18 1
+
+static void call_int18(void *arg)
+{
+	printk(KERN_INFO "Injecting machine check\n");
+	asm("int $0x18");
+}
+
+static long msr_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
+{
+	if (cmd == MSR_INJECT_INT18) {
+		unsigned int cpu = iminor(f->f_path.dentry->d_inode);
+		smp_call_function_single(cpu, call_int18, NULL, 0, 1);
+		return 0;
+	} else
+		return -EINVAL;
+}
+
 /*
  * File operations we support
  */
@@ -131,6 +149,8 @@ static const struct file_operations msr_
 	.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)