Add ValidateDevices function to validate devices parsed from CmdLine

This function runs validation on all devices added via CmdLine, ensuring
they are properly configured before VM startup. It eliminates redundant
individual calls to dev.Validate(), centralizing validation logic.

Also includes a test case to verify ValidateDevices behavior.

Author: vyasgun

cmd/vfkit/main.go

@@ -104,6 +104,10 @@ func newVMConfiguration(opts *cmdline.Options) (*config.VirtualMachine, error) {
 		return nil, err
 	}
 
+	if err := vmConfig.ValidateDevices(); err != nil {
+		return nil, err
+	}
+
 	if err := vmConfig.AddIgnitionFileFromCmdLine(opts.IgnitionPath); err != nil {
 		return nil, fmt.Errorf("failed to add ignition file: %w", err)
 	}

pkg/config/config_test.go

@@ -1,6 +1,9 @@
 package config
 
 import (
+	"os"
+	"os/exec"
+	"path/filepath"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -44,3 +47,24 @@ func TestNetworkBlockDevice_NoDevice(t *testing.T) {
 	nbdItem := vm.NetworkBlockDevice("nbd2")
 	require.Nil(t, nbdItem)
 }
+
+func TestVirtualMachine_ValidateBlockDevices(t *testing.T) {
+	vm := &VirtualMachine{}
+
+	tmpDir := t.TempDir()
+	imagePath := filepath.Join(tmpDir, "disk.qcow2")
+	size := "1G"
+
+	cmd := exec.Command("qemu-img", "create", "-f", "qcow2", imagePath, size)
+	err := cmd.Run()
+	require.NoError(t, err)
+
+	dev, err := VirtioBlkNew(imagePath)
+	require.NoError(t, err)
+	vm.Devices = append(vm.Devices, dev)
+	defer os.Remove(imagePath)
+
+	err = vm.ValidateDevices()
+	require.Error(t, err)
+	require.ErrorContains(t, err, "vfkit does not support qcow2 image format")
+}

pkg/config/virtio.go

@@ -153,6 +153,10 @@ func (v *VirtioBalloon) Validate() error {
 	return nil
 }
 
+func (v *DirectorySharingConfig) Validate() error {
+	return nil
+}
+
 type option struct {
 	key   string
 	value string
@@ -299,7 +303,7 @@ func (dev *VirtioSerial) FromOptions(options []option) error {
 		}
 	}
 
-	return dev.Validate()
+	return nil
 }
 
 // VirtioInputNew creates a new input device for the virtual machine.
@@ -344,7 +348,7 @@ func (dev *VirtioInput) FromOptions(options []option) error {
 			return fmt.Errorf("unknown option for virtio-input devices: %s", option.key)
 		}
 	}
-	return dev.Validate()
+	return nil
 }
 
 // VirtioGPUNew creates a new gpu device for the virtual machine.
@@ -403,7 +407,7 @@ func (dev *VirtioGPU) FromOptions(options []option) error {
 		dev.Height = defaultVirtioGPUResolutionHeight
 	}
 
-	return dev.Validate()
+	return nil
 }
 
 // VirtioNetNew creates a new network device for the virtual machine. It will
@@ -506,7 +510,7 @@ func (dev *VirtioNet) FromOptions(options []option) error {
 		}
 	}
 
-	return dev.Validate()
+	return nil
 }
 
 // VirtioRngNew creates a new random number generator device to feed entropy
@@ -713,10 +717,6 @@ func (dev *VirtioFs) FromOptions(options []option) error {
 	return nil
 }
 
-func (dev *VirtioFs) Validate() error {
-	return nil
-}
-
 // RosettaShareNew RosettaShare creates a new rosetta share for running x86_64 binaries on M1 machines.
 // It will share a directory containing the linux rosetta binaries with the
 // virtual machine. This directory can be mounted in the VM using `mount -t
@@ -762,10 +762,6 @@ func (dev *RosettaShare) FromOptions(options []option) error {
 	return nil
 }
 
-func (dev *RosettaShare) Validate() error {
-	return nil
-}
-
 func networkBlockDeviceNewEmpty() *NetworkBlockDevice {
 	return &NetworkBlockDevice{
 		NetworkBlockStorageConfig: NetworkBlockStorageConfig{