vhost: add vsock compat ioctl

This will allow usage of vsock from 32-bit binaries on a 64-bit
kernel.

Signed-off-by: Sonny Rao <sonnyrao@chromium.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/vsock.c

@@ -699,12 +699,23 @@ static long vhost_vsock_dev_ioctl(struct file *f, unsigned int ioctl,
 	}
 }
 
+#ifdef CONFIG_COMPAT
+static long vhost_vsock_dev_compat_ioctl(struct file *f, unsigned int ioctl,
+					 unsigned long arg)
+{
+	return vhost_vsock_dev_ioctl(f, ioctl, (unsigned long)compat_ptr(arg));
+}
+#endif
+
 static const struct file_operations vhost_vsock_fops = {
 	.owner          = THIS_MODULE,
 	.open           = vhost_vsock_dev_open,
 	.release        = vhost_vsock_dev_release,
 	.llseek		= noop_llseek,
 	.unlocked_ioctl = vhost_vsock_dev_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl   = vhost_vsock_dev_compat_ioctl,
+#endif
 };
 
 static struct miscdevice vhost_vsock_misc = {