drm/i915: Don't request a bug report for unsafe module parameters

Unsafe module parameters are just that, unsafe. If the user is foolish
enough to try them and the kernel breaks, they get to keep both pieces.
Don't ask them to file a bug report if they broke it themselves.

References: https://bugs.freedesktop.org/show_bug.cgi?id=106423
Fixes: d15d7538 ("drm/i915: Tune down init error message due to failure injection")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180506183147.2690-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_drv.c

@@ -101,7 +101,13 @@ __i915_printk(struct drm_i915_private *dev_priv, const char *level,
 		   __builtin_return_address(0), &vaf);
 
 	if (is_error && !shown_bug_once) {
-		dev_notice(kdev, "%s", FDO_BUG_MSG);
+		/*
+		 * Ask the user to file a bug report for the error, except
+		 * if they may have caused the bug by fiddling with unsafe
+		 * module parameters.
+		 */
+		if (!test_taint(TAINT_USER))
+			dev_notice(kdev, "%s", FDO_BUG_MSG);
 		shown_bug_once = true;
 	}