UPSTREAM: <carry>: require configuration file enablement

similarly to what we do for the managed CPU (aka workload partitioning)
feature, introduce a master configuration file
`/etc/kubernetes/openshift-llc-alignment` which needs to be present for
the LLC alignment feature to be activated, in addition to the policy
option being required.

This can be dropped when the feature per  KEP
kubernetes/enhancements#4800 goes beta.

Signed-off-by: Francesco Romani <fromani@redhat.com>

pkg/kubelet/cm/cpumanager/policy_options.go

@@ -59,6 +59,9 @@ func CheckPolicyOptionAvailable(option string) error {
 	if alphaOptions.Has(option) && !utilfeature.DefaultFeatureGate.Enabled(kubefeatures.CPUManagerPolicyAlphaOptions) {
 		return fmt.Errorf("CPU Manager Policy Alpha-level Options not enabled, but option %q provided", option)
 	}
+	if alphaOptions.Has(option) && utilfeature.DefaultFeatureGate.Enabled(kubefeatures.CPUManagerPolicyAlphaOptions) {
+		return checkAlphaPolicyOptionHasEnablement(option)
+	}
 
 	if betaOptions.Has(option) && !utilfeature.DefaultFeatureGate.Enabled(kubefeatures.CPUManagerPolicyBetaOptions) {
 		return fmt.Errorf("CPU Manager Policy Beta-level Options not enabled, but option %q provided", option)

pkg/kubelet/cm/cpumanager/policy_options_enablement.go

@@ -0,0 +1,50 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package cpumanager
+
+import (
+	"fmt"
+
+	"k8s.io/klog/v2"
+	"k8s.io/kubernetes/pkg/kubelet/optenable"
+)
+
+var (
+	forceEnablement bool
+)
+
+func testOnlyForceEnablement() func() {
+	forceEnablement = true
+	return func() {
+		forceEnablement = false
+	}
+}
+
+func checkAlphaPolicyOptionHasEnablement(option string) error {
+	switch option {
+	case PreferAlignByUnCoreCacheOption:
+		klog.InfoS("CPU Manager Policy Alpha level", "option", option, "enablementFile", optenable.LLCAlignment())
+		if optenable.LLCAlignment() {
+			return nil
+		}
+		return fmt.Errorf("CPU Manager Policy Alpha-level Option %q is enabled but miss enablement file", option)
+	}
+	if forceEnablement {
+		return nil
+	}
+	return fmt.Errorf("CPU Manager Policy Alpha-level Option %q is not eligible for enablement", option)
+}

pkg/kubelet/cm/cpumanager/policy_options_test.go

@@ -122,6 +122,10 @@ func TestPolicyOptionsAvailable(t *testing.T) {
 	for _, testCase := range testCases {
 		t.Run(testCase.option, func(t *testing.T) {
 			featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, testCase.featureGate, testCase.featureGateEnable)
+			if testCase.featureGateEnable {
+				revertEnablement := testOnlyForceEnablement()
+				t.Cleanup(revertEnablement)
+			}
 			err := CheckPolicyOptionAvailable(testCase.option)
 			isEnabled := (err == nil)
 			if isEnabled != testCase.expectedAvailable {
@@ -191,6 +195,8 @@ func TestValidateStaticPolicyOptions(t *testing.T) {
 			topoMgrStore := topologymanager.NewFakeManagerWithPolicy(topoMgrPolicy)
 
 			featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, pkgfeatures.CPUManagerPolicyAlphaOptions, true)
+			revertEnablement := testOnlyForceEnablement()
+			t.Cleanup(revertEnablement)
 			policyOpt, _ := NewStaticPolicyOptions(testCase.policyOption)
 			err := ValidateStaticPolicyOptions(policyOpt, testCase.topology, topoMgrStore)
 			gotError := (err != nil)
@@ -238,6 +244,8 @@ func TestPolicyOptionsCompatibility(t *testing.T) {
 	for _, testCase := range testCases {
 		t.Run(testCase.description, func(t *testing.T) {
 			featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, testCase.featureGate, true)
+			revertEnablement := testOnlyForceEnablement()
+			t.Cleanup(revertEnablement)
 			_, err := NewStaticPolicyOptions(testCase.policyOptions)
 			gotError := err != nil
 			if gotError != testCase.expectedErr {

pkg/kubelet/cm/cpumanager/policy_static_test.go

@@ -659,6 +659,8 @@ func runStaticPolicyTestCase(t *testing.T, testCase staticPolicyTest) {
 
 func runStaticPolicyTestCaseWithFeatureGate(t *testing.T, testCase staticPolicyTest) {
 	featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, pkgfeatures.CPUManagerPolicyAlphaOptions, true)
+	revertEnablement := testOnlyForceEnablement()
+	t.Cleanup(revertEnablement)
 	runStaticPolicyTestCase(t, testCase)
 }
 

pkg/kubelet/cm/cpumanager/topology_hints_test.go

@@ -449,6 +449,8 @@ func TestGetPodTopologyHintsWithPolicyOptions(t *testing.T) {
 	for _, testCase := range testCases {
 		t.Run(testCase.description, func(t *testing.T) {
 			featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, pkgfeatures.CPUManagerPolicyAlphaOptions, true)
+			revertEnablement := testOnlyForceEnablement()
+			t.Cleanup(revertEnablement)
 
 			var activePods []*v1.Pod
 			for p := range testCase.assignments {

pkg/kubelet/optenable/optenable.go

@@ -0,0 +1,41 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package optenable
+
+import (
+	"os"
+)
+
+var (
+	// cpumanager: prefer-align-cpus-by-uncorecache
+	llcAlignmentEnabled  bool
+	llcAlignmentFilename = "/etc/kubernetes/openshift-llc-alignment"
+)
+
+func init() {
+	readEnablementFiles()
+}
+
+func readEnablementFiles() {
+	if _, err := os.Stat(llcAlignmentFilename); err == nil {
+		llcAlignmentEnabled = true
+	}
+}
+
+func LLCAlignment() bool {
+	return llcAlignmentEnabled
+}