--- vmwgfx/vmwgfx_driver.c.orig	2016-09-16 03:58:28.611030813 -0700
+++ vmwgfx/vmwgfx_driver.c	2016-09-16 03:53:43.113656575 -0700
@@ -643,13 +643,35 @@
 vmwgfx_scanout_update(int drm_fd, int fb_id, RegionPtr dirty)
 {
     unsigned num_cliprects = REGION_NUM_RECTS(dirty);
-    drmModeClip *clip = alloca(num_cliprects * sizeof(drmModeClip));
+    drmModeClip *clip;
     BoxPtr rect = REGION_RECTS(dirty);
     int i, ret;
 
     if (!num_cliprects)
 	return TRUE;
 
+    if (num_cliprects > 256) {
+	INT32 x1, x2, y1, y2;
+	x1 = rect->x1;
+	y1 = rect->y1;
+	x2 = rect->x2;
+	y2 = rect->y2;
+	rect++;
+	for (i = 1; i < num_cliprects; i++, rect++) {
+	    x1 = min(x1, rect->x1);
+	    y1 = min(y1, rect->y1);
+	    x2 = max(x2, rect->x2);
+	    y2 = max(y2, rect->y2);
+	}
+	num_cliprects = 1;
+	rect = REGION_RECTS(dirty);
+	rect->x1 = x1;
+	rect->y1 = y1;
+	rect->x2 = x2;
+	rect->y2 = y2;
+    }
+
+    clip = alloca(num_cliprects * sizeof(drmModeClip));
     for (i = 0; i < num_cliprects; i++, rect++) {
 	clip[i].x1 = rect->x1;
 	clip[i].y1 = rect->y1;