linux-kernel - [PATCH v2 8/9] perf/x86/intel: Shadow MSR_ARCH_PERFMON_FIXED_CTR

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Date:   Mon, 29 Aug 2022 12:10:07 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     x86@...nel.org, kan.liang@...ux.intel.com, eranian@...gle.com,
        ravi.bangoria@....com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        acme@...nel.org, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        namhyung@...nel.org
Subject: [PATCH v2 8/9] perf/x86/intel: Shadow MSR_ARCH_PERFMON_FIXED_CTR_CTRL

Less RDMSR is more better.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/events/intel/core.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -2405,6 +2405,8 @@ static inline void intel_clear_masks(str
 	__clear_bit(idx, (unsigned long *)&cpuc->intel_cp_status);
 }
 
+static DEFINE_PER_CPU(u64, intel_fixed_ctrl);
+
 static void intel_pmu_disable_fixed(struct perf_event *event)
 {
 	struct hw_perf_event *hwc = &event->hw;
@@ -2426,8 +2428,9 @@ static void intel_pmu_disable_fixed(stru
 	intel_clear_masks(event, idx);
 
 	mask = 0xfULL << ((idx - INTEL_PMC_IDX_FIXED) * 4);
-	rdmsrl(hwc->config_base, ctrl_val);
+	ctrl_val = this_cpu_read(intel_fixed_ctrl);
 	ctrl_val &= ~mask;
+	this_cpu_write(intel_fixed_ctrl, ctrl_val);
 	wrmsrl(hwc->config_base, ctrl_val);
 }
 
@@ -2746,9 +2749,10 @@ static void intel_pmu_enable_fixed(struc
 		mask |= ICL_FIXED_0_ADAPTIVE << (idx * 4);
 	}
 
-	rdmsrl(hwc->config_base, ctrl_val);
+	ctrl_val = this_cpu_read(intel_fixed_ctrl);
 	ctrl_val &= ~mask;
 	ctrl_val |= bits;
+	this_cpu_write(intel_fixed_ctrl, ctrl_val);
 	wrmsrl(hwc->config_base, ctrl_val);
 }