x86/cpufeatures: Add detection of L1D cache flush support.

336996-Speculative-Execution-Side-Channel-Mitigations.pdf defines a new MSR
(IA32_FLUSH_CMD) which is detected by CPUID.7.EDX[28]=1 bit being set.

This new MSR "gives software a way to invalidate structures with finer
granularity than other architectual methods like WBINVD."

A copy of this document is available at
  https://bugzilla.kernel.org/show_bug.cgi?id=199511

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index f41cf9d..64aaa3f 100644 (file)
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -342,6 +342,7 @@
 #define X86_FEATURE_PCONFIG            (18*32+18) /* Intel PCONFIG */
 #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_FLUSH_L1D          (18*32+28) /* Flush L1D cache */
 #define X86_FEATURE_ARCH_CAPABILITIES  (18*32+29) /* IA32_ARCH_CAPABILITIES MSR (Intel) */
 #define X86_FEATURE_SPEC_CTRL_SSBD     (18*32+31) /* "" Speculative Store Bypass Disable */