From e84ead287e115a90171c864eb1e05b9918e8d2cd Mon Sep 17 00:00:00 2001
From: Francesco Romani <fromani@redhat.com>
Date: Tue, 29 Oct 2024 17:31:26 +0100
Subject: [PATCH] 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.

Signed-off-by: Francesco Romani <fromani@redhat.com>
---
 pkg/kubelet/cm/cpumanager/policy_static.go | 17 +++++++-
 pkg/kubelet/llcalign/llcalign.go           | 46 ++++++++++++++++++++++
 2 files changed, 62 insertions(+), 1 deletion(-)
 create mode 100644 pkg/kubelet/llcalign/llcalign.go

diff --git a/pkg/kubelet/cm/cpumanager/policy_static.go b/pkg/kubelet/cm/cpumanager/policy_static.go
index 899c4dd7de5d8..38d8659d97d14 100644
--- a/pkg/kubelet/cm/cpumanager/policy_static.go
+++ b/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", "llcAlignment", 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
+}
diff --git a/pkg/kubelet/llcalign/llcalign.go b/pkg/kubelet/llcalign/llcalign.go
new file mode 100644
index 0000000000000..11dcf0f18bfe6
--- /dev/null
+++ b/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
+}