drm/i915: Create a global list of vms

After we plumb our code to support multiple address spaces (VMs), there
are a few situations where we want to be able to traverse the list of
all address spaces in the system. Cases like eviction, or error state
collection are obvious example.

v2: Delete the global link instead of the list head. While this in and
of itself shouldn't be really be a problem, doing this allows us to WARN
on an non-empty list, which is a problem. (Daniel)

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 5dd4fa5..fd52de7 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1492,6 +1492,10 @@
 
 	i915_dump_device_info(dev_priv);
 
+	INIT_LIST_HEAD(&dev_priv->vm_list);
+	INIT_LIST_HEAD(&dev_priv->gtt.base.global_link);
+	list_add(&dev_priv->gtt.base.global_link, &dev_priv->vm_list);
+
 	if (i915_get_bridge_dev(dev)) {
 		ret = -EIO;
 		goto free_priv;
@@ -1758,6 +1762,8 @@
 			i915_free_hws(dev);
 	}
 
+	list_del(&dev_priv->gtt.base.global_link);
+	WARN_ON(!list_empty(&dev_priv->vm_list));
 	drm_mm_takedown(&dev_priv->gtt.base.mm);
 	if (dev_priv->regs != NULL)
 		pci_iounmap(dev->pdev, dev_priv->regs);