Merge pull request kubevirt#6236 from kubevirt-bot/cherry-pick-6190-t…

…o-release-0.44

[release-0.44] Avoid setting ownership for /dev/kvm in emulation mode

pkg/util/util.go

@@ -2,6 +2,7 @@ package util
 
 import (
 	"fmt"
+	"os"
 	"strings"
 
 	v1 "kubevirt.io/client-go/api/v1"
@@ -81,6 +82,23 @@ func NeedVirtioNetDevice(vmi *v1.VirtualMachineInstance, useEmulation bool) bool
 	return false
 }
 
+// UseSoftwareEmulationForDevice determines whether to fallback to software emulation for the given device.
+// This happens when the given device doesn't exist, and software emulation is enabled.
+func UseSoftwareEmulationForDevice(devicePath string, useEmulation bool) (bool, error) {
+	if !useEmulation {
+		return false, nil
+	}
+
+	_, err := os.Stat(devicePath)
+	if err == nil {
+		return false, nil
+	}
+	if os.IsNotExist(err) {
+		return true, nil
+	}
+	return false, err
+}
+
 func ResourceNameToEnvVar(prefix string, resourceName string) string {
 	varName := strings.ToUpper(resourceName)
 	varName = strings.Replace(varName, "/", "_", -1)

pkg/virt-handler/vm.go

@@ -2414,13 +2414,9 @@ func (d *VirtualMachineController) vmUpdateHelperMigrationTarget(origVMI *v1.Vir
 
 	}
 
-	res, err := d.podIsolationDetector.Detect(vmi)
+	err = d.claimKVMDeviceOwnership(vmi)
 	if err != nil {
-		return err
-	}
-
-	if err := diskutils.DefaultOwnershipManager.SetFileOwnership(path.Join(res.MountRoot(), "dev", "kvm")); err != nil {
-		return err
+		return fmt.Errorf("failed to set up file ownership for /dev/kvm: %v", err)
 	}
 
 	if virtutil.IsNonRootVMI(vmi) {
@@ -2504,12 +2500,9 @@ func (d *VirtualMachineController) vmUpdateHelperDefault(origVMI *v1.VirtualMach
 
 		}
 
-		res, err := d.podIsolationDetector.Detect(vmi)
+		err = d.claimKVMDeviceOwnership(vmi)
 		if err != nil {
-			return err
-		}
-		if err := diskutils.DefaultOwnershipManager.SetFileOwnership(path.Join(res.MountRoot(), "dev", "kvm")); err != nil {
-			return err
+			return fmt.Errorf("failed to set up file ownership for /dev/kvm: %v", err)
 		}
 
 		if virtutil.IsNonRootVMI(vmi) {
@@ -2772,6 +2765,22 @@ func (d *VirtualMachineController) isHostModelMigratable(vmi *v1.VirtualMachineI
 	return nil
 }
 
+func (d *VirtualMachineController) claimKVMDeviceOwnership(vmi *v1.VirtualMachineInstance) error {
+	isolation, err := d.podIsolationDetector.Detect(vmi)
+	if err != nil {
+		return err
+	}
+
+	kvmPath := path.Join(isolation.MountRoot(), "dev", "kvm")
+
+	softwareEmulation, err := util.UseSoftwareEmulationForDevice(kvmPath, d.clusterConfig.IsUseEmulation())
+	if err != nil || softwareEmulation {
+		return err
+	}
+
+	return diskutils.DefaultOwnershipManager.SetFileOwnership(kvmPath)
+}
+
 func nodeHasHostModelLabel(node *k8sv1.Node) bool {
 	for key, _ := range node.Labels {
 		if strings.HasPrefix(key, v1.HostModelCPULabel) {

pkg/virt-launcher/virtwrap/converter/converter.go

@@ -1136,26 +1136,28 @@ func Convert_v1_VirtualMachineInstance_To_api_Domain(vmi *v1.VirtualMachineInsta
 		CPUs:      cpuCount,
 	}
 
-	if _, err := os.Stat("/dev/kvm"); os.IsNotExist(err) {
-		if c.UseEmulation {
-			logger := log.DefaultLogger()
-			logger.Infof("Hardware emulation device '/dev/kvm' not present. Using software emulation.")
-			domain.Spec.Type = "qemu"
-		} else {
-			return fmt.Errorf("hardware emulation device '/dev/kvm' not present")
-		}
+	kvmPath := "/dev/kvm"
+	if softwareEmulation, err := util.UseSoftwareEmulationForDevice(kvmPath, c.UseEmulation); err != nil {
+		return err
+	} else if softwareEmulation {
+		logger := log.DefaultLogger()
+		logger.Infof("Hardware emulation device '%s' not present. Using software emulation.", kvmPath)
+		domain.Spec.Type = "qemu"
+	} else if _, err := os.Stat(kvmPath); os.IsNotExist(err) {
+		return fmt.Errorf("hardware emulation device '%s' not present", kvmPath)
 	} else if err != nil {
 		return err
 	}
 
 	virtioNetProhibited := false
-	if _, err := os.Stat("/dev/vhost-net"); os.IsNotExist(err) {
-		if c.UseEmulation {
-			logger := log.DefaultLogger()
-			logger.Infof("In-kernel virtio-net device emulation '/dev/vhost-net' not present. Falling back to QEMU userland emulation.")
-		} else {
-			virtioNetProhibited = true
-		}
+	vhostNetPath := "/dev/vhost-net"
+	if softwareEmulation, err := util.UseSoftwareEmulationForDevice(vhostNetPath, c.UseEmulation); err != nil {
+		return err
+	} else if softwareEmulation {
+		logger := log.DefaultLogger()
+		logger.Infof("In-kernel virtio-net device emulation '%s' not present. Falling back to QEMU userland emulation.", vhostNetPath)
+	} else if _, err := os.Stat(vhostNetPath); os.IsNotExist(err) {
+		virtioNetProhibited = true
 	} else if err != nil {
 		return err
 	}