Add notes about running things as root.
diff --git a/README b/README
index 3f72927..9992d33 100644
--- a/README
+++ b/README
@@ -23,3 +23,9 @@
built with the 2D driver but not shipped. Some distros were hacking
up the 2D build to ship them. Instead, here's a separate package for
people debugging the driver.
+
+Note that most of these tools must be run as root. Several tools require
+MMIO register access (which may be denied if CONFIG_STRICT_DEVMEM is enabled).
+When an X Server is running, benchmarks and tests clients won't be able to
+run due to being unable to authenticate against it, unless you run them as
+root.