linux-kernel - [PATCH 2/4] perf/x86/intel: Do not deploy workaround when TSX is deprecated

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Date:   Wed, 9 Jun 2021 14:12:38 -0700
From:   Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>
Cc:     Jonathan Corbet <corbet@....net>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Maciej W. Rozycki" <macro@...am.me.uk>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Tony Luck <tony.luck@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kyung Min Park <kyung.min.park@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Krish Sadhukhan <krish.sadhukhan@...cle.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Joerg Roedel <jroedel@...e.de>,
        Victor Ding <victording@...gle.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Dave Hansen <dave.hansen@...el.com>,
        Mike Rapoport <rppt@...nel.org>,
        Anthony Steinhauser <asteinhauser@...gle.com>,
        Anand K Mistry <amistry@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Nick Desaulniers <ndesaulniers@...ogle.com>,
        Joe Perches <joe@...ches.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: [PATCH 2/4] perf/x86/intel: Do not deploy workaround when TSX is
 deprecated

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@...ux.intel.com>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Tested-by: Neelima Krishnan <neelima.krishnan@...el.com>
---
 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