linux-kernel - [tip: x86/cpu] x86/events/intel: Do not deploy TSX force abort workaround when TSX is deprecated

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Date:   Tue, 15 Jun 2021 17:14:36 -0000
From:   "tip-bot2 for Pawan Gupta" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Borislav Petkov <bp@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andi Kleen <ak@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Neelima Krishnan <neelima.krishnan@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/cpu] x86/events/intel: Do not deploy TSX force abort
 workaround when TSX is deprecated

The following commit has been merged into the x86/cpu branch of tip:

Commit-ID:     ad3c2e174938d72fded674acead42e2464a3b460
Gitweb:        https://git.kernel.org/tip/ad3c2e174938d72fded674acead42e2464a3b460
Author:        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
AuthorDate:    Mon, 14 Jun 2021 14:13:23 -07:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Tue, 15 Jun 2021 17:36:03 +02:00

x86/events/intel: Do not deploy TSX force abort workaround when TSX is deprecated

Earlier workaround added by

  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] [ bp: Look for document ID 604224, "Performance Monitoring Impact
      of Intel Transactional Synchronization Extension Memory". Since
      there's no way for us to have stable links to documents... ]

 [ bp: Massage comment. ]

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Tested-by: Neelima Krishnan <neelima.krishnan@...el.com>
Link: https://lkml.kernel.org/r/e4d410f786946280ced02dd07c74e0a74f1d10cb.1623704845.git-series.pawan.kumar.gupta@linux.intel.com
---
 arch/x86/events/intel/core.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 2521d03..062bf89 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -6015,7 +6015,13 @@ __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
+		 * workaround when microcode has not enabled 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;