drm/i915: taint the kernel if unsafe module parameters are set

Taint the kernel if the semaphores, enable_rc6, enable_fbc, or ppgtt
module parameters are modified. These module parameters are for
debugging and testing only, and should never be changed from their
platform specific default values by the users. We do not provide support
for people enabling all the experimental features. Make this clear by
tainting the kernel if the parameters are set.

Signed-off-by: Jani Nikula <[email protected]>
Signed-off-by: Rusty Russell <[email protected]>

drivers/gpu/drm/i915/i915_params.c

@@ -66,20 +66,20 @@ module_param_named(powersave, i915.powersave, int, 0600);
 MODULE_PARM_DESC(powersave,
 	"Enable powersavings, fbc, downclocking, etc. (default: true)");
 
-module_param_named(semaphores, i915.semaphores, int, 0400);
+module_param_named_unsafe(semaphores, i915.semaphores, int, 0400);
 MODULE_PARM_DESC(semaphores,
 	"Use semaphores for inter-ring sync "
 	"(default: -1 (use per-chip defaults))");
 
-module_param_named(enable_rc6, i915.enable_rc6, int, 0400);
+module_param_named_unsafe(enable_rc6, i915.enable_rc6, int, 0400);
 MODULE_PARM_DESC(enable_rc6,
 	"Enable power-saving render C-state 6. "
 	"Different stages can be selected via bitmask values "
 	"(0 = disable; 1 = enable rc6; 2 = enable deep rc6; 4 = enable deepest rc6). "
 	"For example, 3 would enable rc6 and deep rc6, and 7 would enable everything. "
 	"default: -1 (use per-chip default)");
 
-module_param_named(enable_fbc, i915.enable_fbc, int, 0600);
+module_param_named_unsafe(enable_fbc, i915.enable_fbc, int, 0600);
 MODULE_PARM_DESC(enable_fbc,
 	"Enable frame buffer compression for power savings "
 	"(default: -1 (use per-chip default))");
@@ -113,7 +113,7 @@ MODULE_PARM_DESC(enable_hangcheck,
 	"WARNING: Disabling this can cause system wide hangs. "
 	"(default: true)");
 
-module_param_named(enable_ppgtt, i915.enable_ppgtt, int, 0400);
+module_param_named_unsafe(enable_ppgtt, i915.enable_ppgtt, int, 0400);
 MODULE_PARM_DESC(enable_ppgtt,
 	"Override PPGTT usage. "
 	"(-1=auto [default], 0=disabled, 1=aliasing, 2=full)");