x86/intel_rdt: Add command line parameter to control L2_CDP

L2 CDP can be controlled by kernel parameter "rdt=".
If "rdt=l2cdp", L2 CDP is turned on.
If "rdt=!l2cdp", L2 CDP is turned off.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "Ravi V Shankar" <ravi.v.shankar@intel.com>
Cc: "Tony Luck" <tony.luck@intel.com>
Cc: Vikas" <vikas.shivappa@intel.com>
Cc: Sai Praneeth" <sai.praneeth.prakhya@intel.com>
Cc: Reinette" <reinette.chatre@intel.com>
Link: https://lkml.kernel.org/r/1513810644-78015-7-git-send-email-fenghua.yu@intel.com

Documentation/admin-guide/kernel-parameters.txt

@@ -3682,7 +3682,8 @@
 
 	rdt=		[HW,X86,RDT]
 			Turn on/off individual RDT features. List is:
-			cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, mba.
+			cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
+			mba.
 			E.g. to turn on cmt and turn off mba use:
 				rdt=cmt,!mba
 

arch/x86/kernel/cpu/intel_rdt.c

@@ -691,6 +691,7 @@ enum {
 	RDT_FLAG_L3_CAT,
 	RDT_FLAG_L3_CDP,
 	RDT_FLAG_L2_CAT,
+	RDT_FLAG_L2_CDP,
 	RDT_FLAG_MBA,
 };
 
@@ -713,6 +714,7 @@ static struct rdt_options rdt_options[]  __initdata = {
 	RDT_OPT(RDT_FLAG_L3_CAT,    "l3cat",	X86_FEATURE_CAT_L3),
 	RDT_OPT(RDT_FLAG_L3_CDP,    "l3cdp",	X86_FEATURE_CDP_L3),
 	RDT_OPT(RDT_FLAG_L2_CAT,    "l2cat",	X86_FEATURE_CAT_L2),
+	RDT_OPT(RDT_FLAG_L2_CDP,    "l2cdp",	X86_FEATURE_CDP_L2),
 	RDT_OPT(RDT_FLAG_MBA,	    "mba",	X86_FEATURE_MBA),
 };
 #define NUM_RDT_OPTIONS ARRAY_SIZE(rdt_options)