[PATCH v2 2/3] perf/x86/intel: Do not deploy workaround when TSX is deprecated

[Pawan Gupta]

Earlier workaround added by commit 400816f60c54 ("perf/x86/intel:
Implement support for TSX Force Abort") for perf counter interactions
[1] are not required on some client systems which received a microcode
update that deprecates TSX.

Bypass the perf workaround when such microcode is enumerated.

[1] Performance Monitoring Impact of Intel® Transactional Synchronization Extension Memory
    http://cdrdv2.intel.com/v1/dl/getContent/604224 (Document ID 604224)

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
Tested-by: Neelima Krishnan <neelima.krishnan@xxxxxxxxx>
---
 arch/x86/events/intel/core.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index e28892270c58..b599a30fcc7d 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -6015,7 +6015,15 @@ __init int intel_pmu_init(void)
 		tsx_attr = hsw_tsx_events_attrs;
 		intel_pmu_pebs_data_source_skl(pmem);
 
-		if (boot_cpu_has(X86_FEATURE_TSX_FORCE_ABORT)) {
+		/* Processors with CPUID.RTM_ALWAYS_ABORT have TSX deprecated by
+		 * default. TSX force abort hooks are not required on these
+		 * systems.
+		 *
+		 * Only deploy the workaround when older microcode is detected
+		 * i.e. !X86_FEATURE_RTM_ALWAYS_ABORT.
+		 */
+		if (boot_cpu_has(X86_FEATURE_TSX_FORCE_ABORT) &&
+		   !boot_cpu_has(X86_FEATURE_RTM_ALWAYS_ABORT)) {
 			x86_pmu.flags |= PMU_FL_TFA;
 			x86_pmu.get_event_constraints = tfa_get_event_constraints;
 			x86_pmu.enable_all = intel_tfa_pmu_enable_all;
-- 
git-series 0.9.1