diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index 8d0cbf10cbba6d017be84d48c1648ead6aa0455e..2bc6c80065ce3c5262dc73a09b8a7033b97b4e96 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -3684,7 +3684,9 @@ int num_ioctls;</synopsis>
 	    </para></listitem>
             <listitem><para>
 	      DRM_UNLOCKED - The ioctl handler will be called without locking
-	      the DRM global mutex
+	      the DRM global mutex. This is the enforced default for kms drivers
+	      (i.e. using the DRIVER_MODESET flag) and hence shouldn't be used
+	      any more for new drivers.
 	    </para></listitem>
 	  </itemizedlist>
 	</para>
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 530c501422fd696ef3c5a1c1e526728b9d709ed0..8ce2a0c591165018c49392e7ad2b828a1fb3b94b 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -691,13 +691,16 @@ long drm_ioctl(struct file *filp,
 	char stack_kdata[128];
 	char *kdata = NULL;
 	unsigned int usize, asize, drv_size;
+	bool is_driver_ioctl;
 
 	dev = file_priv->minor->dev;
 
 	if (drm_device_is_unplugged(dev))
 		return -ENODEV;
 
-	if (nr >= DRM_COMMAND_BASE && nr < DRM_COMMAND_END) {
+	is_driver_ioctl = nr >= DRM_COMMAND_BASE && nr < DRM_COMMAND_END;
+
+	if (is_driver_ioctl) {
 		/* driver ioctl */
 		if (nr - DRM_COMMAND_BASE >= dev->driver->num_ioctls)
 			goto err_i1;
@@ -756,7 +759,10 @@ long drm_ioctl(struct file *filp,
 		memset(kdata, 0, usize);
 	}
 
-	if (ioctl->flags & DRM_UNLOCKED)
+	/* Enforce sane locking for kms driver ioctls. Core ioctls are
+	 * too messy still. */
+	if ((drm_core_check_feature(dev, DRIVER_MODESET) && is_driver_ioctl) ||
+	    (ioctl->flags & DRM_UNLOCKED))
 		retcode = func(dev, kdata, file_priv);
 	else {
 		mutex_lock(&drm_global_mutex);