libcontainer/intelrdt: verify ClosID existence

Check that the ClosID directory pre-exists if no L3 or MB schema has
been specified. Conform with the following line from runtime-spec
(config-linux):

  If closID is set, and neither of l3CacheSchema and memBwSchema are
  set, runtime MUST check if corresponding pre-configured directory
  closID is present in mounted resctrl. If such pre-configured directory
  closID exists, runtime MUST assign container to this closID and
  generate an error if directory does not exist.

Add a TODO note for verifying existing schemata against L3/MB
parameters.

Signed-off-by: Markus Lehtonen <markus.lehtonen@intel.com>

libcontainer/intelrdt/intelrdt.go

@@ -205,7 +205,6 @@ var (
 )
 
 type intelRdtData struct {
-	root   string
 	config *configs.Config
 }
 
@@ -548,6 +547,14 @@ func (m *intelRdtManager) Apply(pid int) (err error) {
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
+	if m.config.IntelRdt.ClosID != "" && m.config.IntelRdt.L3CacheSchema == "" && m.config.IntelRdt.MemBwSchema == "" {
+		// Check that the CLOS exists, i.e. it has been pre-configured to
+		// conform with the runtime spec
+		if _, err := os.Stat(path); err != nil {
+			return fmt.Errorf("clos dir not accessible (must be pre-created when l3CacheSchema and memBwSchema are empty): %w", err)
+		}
+	}
+
 	if err := os.MkdirAll(path, 0o755); err != nil {
 		return newLastCmdError(err)
 	}
@@ -723,6 +730,12 @@ func (m *intelRdtManager) Set(container *configs.Config) error {
 		l3CacheSchema := container.IntelRdt.L3CacheSchema
 		memBwSchema := container.IntelRdt.MemBwSchema
 
+		// TODO: verify that l3CacheSchema and/or memBwSchema match the
+		// existing schemata if ClosID has been specified. This is a more
+		// involved than reading the file and doing plain string comparison as
+		// the value written in does not necessarily match what gets read out
+		// (leading zeros, cache id ordering etc).
+
 		// Write a single joint schema string to schemata file
 		if l3CacheSchema != "" && memBwSchema != "" {
 			if err := writeFile(path, "schemata", l3CacheSchema+"\n"+memBwSchema); err != nil {

libcontainer/intelrdt/intelrdt_test.go

@@ -5,6 +5,8 @@ package intelrdt
 import (
 	"errors"
 	"io"
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 )
@@ -111,6 +113,35 @@ func TestIntelRdtSetMemBwScSchema(t *testing.T) {
 	}
 }
 
+func TestApply(t *testing.T) {
+	helper := NewIntelRdtTestUtil(t)
+
+	const closID = "test-clos"
+
+	helper.IntelRdtData.config.IntelRdt.ClosID = closID
+	intelrdt := NewManager(helper.IntelRdtData.config, "", helper.IntelRdtPath)
+	if err := intelrdt.Apply(1234); err == nil {
+		t.Fatal("unexpected success when applying pid")
+	}
+	if _, err := os.Stat(filepath.Join(helper.IntelRdtPath, closID)); err == nil {
+		t.Fatal("closid dir should not exist")
+	}
+
+	// Dir should be created if some schema has been specified
+	intelrdt.(*intelRdtManager).config.IntelRdt.L3CacheSchema = "L3:0=f"
+	if err := intelrdt.Apply(1235); err != nil {
+		t.Fatalf("Apply() failed: %v", err)
+	}
+
+	pids, err := getIntelRdtParamString(intelrdt.GetPath(), "tasks")
+	if err != nil {
+		t.Fatalf("failed to read tasks file: %v", err)
+	}
+	if pids != "1235" {
+		t.Fatalf("unexpected tasks file, expected '1235', got %q", pids)
+	}
+}
+
 const (
 	mountinfoValid = `18 40 0:18 / /sys rw,nosuid,nodev,noexec,relatime shared:6 - sysfs sysfs rw
 19 40 0:3 / /proc rw,nosuid,nodev,noexec,relatime shared:5 - proc proc rw

libcontainer/intelrdt/util_test.go

@@ -30,9 +30,9 @@ func NewIntelRdtTestUtil(t *testing.T) *intelRdtTestUtil {
 		config: &configs.Config{
 			IntelRdt: &configs.IntelRdt{},
 		},
-		root: t.TempDir(),
 	}
-	testIntelRdtPath := filepath.Join(d.root, "resctrl")
+	intelRdtRoot = t.TempDir()
+	testIntelRdtPath := filepath.Join(intelRdtRoot, "resctrl")
 
 	// Ensure the full mock Intel RDT "resource control" filesystem path exists
 	if err := os.MkdirAll(testIntelRdtPath, 0o755); err != nil {