Insert extra checks into the GEM internals

configname: CONFIG_DRM_I915_DEBUG_GEM

Linux Kernel Configuration
└─>Device Drivers
└─>Graphics support
└─>drm/i915 Debugging
└─>Insert extra checks into the GEM internals
In linux kernel since version 4.1 (release Date: 2015-06-21)  
Enable extra sanity checks (including BUGs) along the GEM driver
paths that may slow the system down and if hit hang the machine.

Recommended for driver developers only.

If in doubt, say "N".