[PATCH 2/4] 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

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 | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index e28892270c58..b5953e1e59a2 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -6016,10 +6016,24 @@ __init int intel_pmu_init(void)
 		intel_pmu_pebs_data_source_skl(pmem);
 
 		if (boot_cpu_has(X86_FEATURE_TSX_FORCE_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;
-			x86_pmu.commit_scheduling = intel_tfa_commit_scheduling;
+			u64 msr;
+
+			rdmsrl(MSR_TSX_FORCE_ABORT, msr);
+			/* Systems that enumerate CPUID.RTM_ALWAYS_ABORT or
+			 * support MSR_TSX_FORCE_ABORT[SDV_ENABLE_RTM] bit have
+			 * TSX deprecated by default. TSX force abort hooks are
+			 * not required on these systems.
+			 *
+			 * Only deploy the workaround when older microcode is
+			 * detected.
+			 */
+			if (!boot_cpu_has(X86_FEATURE_RTM_ALWAYS_ABORT) &&
+			    !(msr & MSR_TFA_SDV_ENABLE_RTM)) {
+				x86_pmu.flags |= PMU_FL_TFA;
+				x86_pmu.get_event_constraints = tfa_get_event_constraints;
+				x86_pmu.enable_all = intel_tfa_pmu_enable_all;
+				x86_pmu.commit_scheduling = intel_tfa_commit_scheduling;
+			}
 		}
 
 		pr_cont("Skylake events, ");
-- 
git-series 0.9.1