libcontainer/intelrdt: fix CMT feature check

Intel RDT sub-features can be selectively disabled or enabled by kernel
command line. See "rdt=" option details in kernel document:
https://www.kernel.org/doc/Documentation/admin-guide/kernel-parameters.txt

But Cache Monitoring Technology (CMT) feature is not correctly checked
in init() and getCMTNumaNodeStats() now. If CMT is disabled by kernel
command line (e.g., rdt=!cmt,mbmtotal,mbmlocal,l3cat,mba) while hardware
supports CMT, we may get following error when getting Intel RDT stats:
  runc run c1
  runc events c1
  ERRO[0005] container_linux.go:200: getting container's Intel RDT stats
  caused: open /sys/fs/resctrl/c1/mon_data/mon_L3_00/llc_occupancy: no
  such file or directory

Fix CMT feature check in init() and GetStats() call paths.

Signed-off-by: Xiaochen Shen <[email protected]>

Author: xiaochenshen

libcontainer/intelrdt/cmt.go

@@ -12,11 +12,13 @@ func IsCMTEnabled() bool {
 func getCMTNumaNodeStats(numaPath string) (*CMTNumaNodeStats, error) {
 	stats := &CMTNumaNodeStats{}
 
-	llcOccupancy, err := getIntelRdtParamUint(numaPath, "llc_occupancy")
-	if err != nil {
-		return nil, err
+	if enabledMonFeatures.llcOccupancy {
+		llcOccupancy, err := getIntelRdtParamUint(numaPath, "llc_occupancy")
+		if err != nil {
+			return nil, err
+		}
+		stats.LLCOccupancy = llcOccupancy
 	}
-	stats.LLCOccupancy = llcOccupancy
 
 	return stats, nil
 }

libcontainer/intelrdt/intelrdt.go

@@ -229,16 +229,20 @@ func init() {
 		}
 	}
 
-	if flagsSet.MBMTotal || flagsSet.MBMLocal {
-		if _, err := os.Stat(filepath.Join(intelRdtRoot, "info", "L3_MON")); err == nil {
-			mbmEnabled = true
-			cmtEnabled = true
+	if flagsSet.MBMTotal || flagsSet.MBMLocal || flagsSet.CMT {
+		if _, err := os.Stat(filepath.Join(intelRdtRoot, "info", "L3_MON")); err != nil {
+			return
 		}
-
 		enabledMonFeatures, err = getMonFeatures(intelRdtRoot)
 		if err != nil {
 			return
 		}
+		if enabledMonFeatures.mbmTotalBytes || enabledMonFeatures.mbmLocalBytes {
+			mbmEnabled = true
+		}
+		if enabledMonFeatures.llcOccupancy {
+			cmtEnabled = true
+		}
 	}
 }
 
@@ -305,6 +309,8 @@ type cpuInfoFlags struct {
 	// Memory Bandwidth Monitoring related.
 	MBMTotal bool
 	MBMLocal bool
+
+	CMT bool // Cache Monitoring Technology
 }
 
 func parseCpuInfoFile(path string) (cpuInfoFlags, error) {
@@ -334,6 +340,8 @@ func parseCpuInfoFile(path string) (cpuInfoFlags, error) {
 					infoFlags.MBMTotal = true
 				case "cqm_mbm_local":
 					infoFlags.MBMLocal = true
+				case "cqm_occup_llc":
+					infoFlags.CMT = true
 				}
 			}
 			return infoFlags, nil
@@ -651,9 +659,11 @@ func (m *IntelRdtManager) GetStats() (*Stats, error) {
 		}
 	}
 
-	err = getMonitoringStats(containerPath, stats)
-	if err != nil {
-		return nil, err
+	if IsMBMEnabled() || IsCMTEnabled() {
+		err = getMonitoringStats(containerPath, stats)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	return stats, nil