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 <[email protected]>

Author: ffromani

pkg/kubelet/cm/cpumanager/policy_static.go

@@ -29,6 +29,7 @@ import (
 	"k8s.io/kubernetes/pkg/kubelet/cm/cpumanager/topology"
 	"k8s.io/kubernetes/pkg/kubelet/cm/topologymanager"
 	"k8s.io/kubernetes/pkg/kubelet/cm/topologymanager/bitmask"
+	"k8s.io/kubernetes/pkg/kubelet/llcalign"
 	"k8s.io/kubernetes/pkg/kubelet/managed"
 	"k8s.io/kubernetes/pkg/kubelet/metrics"
 	"k8s.io/kubernetes/pkg/kubelet/types"
@@ -138,6 +139,7 @@ func NewStaticPolicy(topology *topology.CPUTopology, numReservedCPUs int, reserv
 	}
 
 	klog.InfoS("Static policy created with configuration", "options", opts)
+	klog.InfoS("Static policy created with configuration", "llcAlignmentSupportEnabled", llcalign.IsEnabled())
 
 	policy := &staticPolicy{
 		topology:    topology,
@@ -511,7 +513,9 @@ func (p *staticPolicy) takeByTopology(availableCPUs cpuset.CPUSet, numCPUs int)
 		return takeByTopologyNUMADistributed(p.topology, availableCPUs, numCPUs, cpuGroupSize, cpuSortingStrategy)
 	}
 
-	return takeByTopologyNUMAPacked(p.topology, availableCPUs, numCPUs, cpuSortingStrategy, p.options.PreferAlignByUncoreCacheOption)
+	preferAlignByUncoreCacheOption := isAlignByUncoreCacheEnabled(p.options)
+	klog.V(4).InfoS("Taking CPUs", "requested", numCPUs, "llcAlignment", preferAlignByUncoreCacheOption)
+	return takeByTopologyNUMAPacked(p.topology, availableCPUs, numCPUs, cpuSortingStrategy, preferAlignByUncoreCacheOption)
 }
 
 func (p *staticPolicy) GetTopologyHints(s state.State, pod *v1.Pod, container *v1.Container) map[string][]topologymanager.TopologyHint {
@@ -723,3 +727,14 @@ func (p *staticPolicy) getAlignedCPUs(numaAffinity bitmask.BitMask, allocatableC
 
 	return alignedCPUs
 }
+
+func isAlignByUncoreCacheEnabled(options StaticPolicyOptions) bool {
+	if !options.PreferAlignByUncoreCacheOption {
+		return false
+	}
+	if !llcalign.IsEnabled() {
+		klog.V(4).InfoS("isAlignByUncoreCacheEnabled disabled because missing config file")
+		return false
+	}
+	return true
+}

pkg/kubelet/llcalign/llcalign.go

@@ -0,0 +1,46 @@
+/*
+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 llcalign
+
+import (
+	"os"
+)
+
+var (
+	llcAlignmentEnabled  bool
+	llcAlignmentFilename = "/etc/kubernetes/openshift-llc-alignment"
+)
+
+func init() {
+	readEnablementFile()
+}
+
+func readEnablementFile() {
+	if _, err := os.Stat(llcAlignmentFilename); err == nil {
+		llcAlignmentEnabled = true
+	}
+}
+
+// TestOnlySetEnabled allows changing the state of management partition enablement
+// This method MUST NOT be used outside of test code
+func TestOnlySetEnabled(enabled bool) {
+	llcAlignmentEnabled = enabled
+}
+
+func IsEnabled() bool {
+	return llcAlignmentEnabled
+}