x86/cpufeatures: Add Architectural LBRs feature bit

CPUID.(EAX=07H, ECX=0):EDX[19] indicates whether an Intel CPU supports
Architectural LBRs.

The "X86_FEATURE_..., word 18" is already mirrored from CPUID
"0x00000007:0 (EDX)". Add X86_FEATURE_ARCH_LBR under the "word 18"
section.

The feature will appear as "arch_lbr" in /proc/cpuinfo.

The Architectural Last Branch Records (LBR) feature enables recording
of software path history by logging taken branches and other control
flows. The feature will be supported in the perf_events subsystem.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Link: https://lkml.kernel.org/r/1593780569-62993-2-git-send-email-kan.liang@linux.intel.com

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 02dabc9..72ba4c5 100644 (file)
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -366,6 +366,7 @@
 #define X86_FEATURE_MD_CLEAR           (18*32+10) /* VERW clears CPU buffers */
 #define X86_FEATURE_TSX_FORCE_ABORT    (18*32+13) /* "" TSX_FORCE_ABORT */
 #define X86_FEATURE_PCONFIG            (18*32+18) /* Intel PCONFIG */
+#define X86_FEATURE_ARCH_LBR           (18*32+19) /* Intel ARCH LBR */
 #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 */