x86/cpufeatures: Add X86_FEATURE_RDS

Add the CPU feature bit CPUID.7.0.EDX[31] which indicates whether the CPU
supports Reduced Data Speculation.

[ tglx: Split it out from a later patch ]

Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Ingo Molnar <[email protected]>

Orabug: 28034177
CVE: CVE-2018-3639

(cherry picked from commit 0cc5fa0)
Signed-off-by: Konrad Rzeszutek Wilk <[email protected]>
Tested-by: Mihai Carabas <[email protected]>
Reviewed-by: Mihai Carabas <[email protected]>
Reviewed-by: John Haxby <[email protected]>
Reviewed-by: Darren Kenny <[email protected]>

Author: konradwilk

arch/x86/include/asm/cpufeatures.h

@@ -335,6 +335,7 @@
 #define X86_FEATURE_SPEC_CTRL		(18*32+26) /* "" Speculation Control (IBRS + IBPB) */
 #define X86_FEATURE_INTEL_STIBP		(18*32+27) /* "" Single Thread Indirect Branch Predictors */
 #define X86_FEATURE_ARCH_CAPABILITIES	(18*32+29) /* IA32_ARCH_CAPABILITIES MSR (Intel) */
+#define X86_FEATURE_RDS			(18*32+31) /* Reduced Data Speculation */
 
 /*
  * BUG word(s)