feat: Validate rootvol and kernel spec in webhook

The previous commit made these fields optional, but we need to verify
that at least some kernel and root volume information is set.

This validation will check whether the short syntax for kernel and root
volume config are set, and if not, will validate that long syntax fields
are provided. Errors are returned if not.

api/v1alpha1/microvmmachine_webhook.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"reflect"
 
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/util/validation/field"
 	ctrl "sigs.k8s.io/controller-runtime"
@@ -34,7 +35,15 @@ var (
 
 // ValidateCreate implements webhook.Validator so a webhook will be registered for the type.
 func (r *MicrovmMachine) ValidateCreate() error {
-	return nil
+	var allErrs field.ErrorList
+
+	allErrs = append(allErrs, r.Spec.MicrovmSpec.Validate()...)
+
+	if len(allErrs) == 0 {
+		return nil
+	}
+
+	return apierrors.NewInvalid(r.GroupVersionKind().GroupKind(), r.Name, allErrs)
 }
 
 // ValidateDelete implements webhook.Validator so a webhook will be registered for the type.

api/v1alpha1/types.go

@@ -20,15 +20,15 @@ type MicrovmSpec struct {
 	MemoryMb int64 `json:"memoryMb"`
 
 	// RootVolume specifies the volume to use for the root of the microvm.
-	// +kubebuilder:validation:Required
+	// +optional
 	RootVolume Volume `json:"rootVolume"`
 
 	// AdditionalVolumes specifies additional non-root volumes to attach to the microvm.
 	// +optional
 	AdditionalVolumes []Volume `json:"volumes,omitempty"`
 
 	// Kernel specifies the kernel and its arguments to use.
-	// +kubebuilder:validation:Required
+	// +optional
 	Kernel ContainerFileSource `json:"kernel"`
 
 	// KernelCmdLine are the additional args to use for the kernel cmdline.

api/v1alpha1/validate.go

@@ -18,3 +18,33 @@ func (p *Placement) Validate() []*field.Error {
 
 	return errs
 }
+
+func (s *MicrovmSpec) Validate() []*field.Error {
+	var errs field.ErrorList
+
+	if s.OsVersion == "" {
+		if s.RootVolume.ID == "" {
+			errs = append(errs,
+				field.Required(field.NewPath("spec", "rootVolume", "id"), "must be set if osVersion is omitted"))
+		}
+
+		if s.RootVolume.Image == "" {
+			errs = append(errs,
+				field.Required(field.NewPath("spec", "rootVolume", "image"), "must be set if osVersion is omitted"))
+		}
+	}
+
+	if s.KernelVersion == "" {
+		if s.Kernel.Image == "" {
+			errs = append(errs,
+				field.Required(field.NewPath("spec", "kernel", "image"), "must be set if kernelVersion is omitted"))
+		}
+
+		if s.Kernel.Filename == "" {
+			errs = append(errs,
+				field.Required(field.NewPath("spec", "kernel", "filename"), "must be set if kernelVersion is omitted"))
+		}
+	}
+
+	return errs
+}

config/crd/bases/infrastructure.cluster.x-k8s.io_microvmmachines.yaml

@@ -198,10 +198,8 @@ spec:
                   type: object
                 type: array
             required:
-            - kernel
             - memoryMb
             - networkInterfaces
-            - rootVolume
             - vcpu
             type: object
           status:

config/crd/bases/infrastructure.cluster.x-k8s.io_microvmmachinetemplates.yaml

@@ -241,10 +241,8 @@ spec:
                           type: object
                         type: array
                     required:
-                    - kernel
                     - memoryMb
                     - networkInterfaces
-                    - rootVolume
                     - vcpu
                     type: object
                 required: