HCP Packer Registry Support + CD-ROM Bus Portability

[dejo-oyelese]

Summary

This PR adds native HCP Packer registry integration to the kubevirt-iso
builder and fixes a pre-existing bug where Linux CD-ROM disk devices had no
bus type set, causing builds to fail on arm64 clusters.

---

Changes

1. HCP Packer registry support (10f464d)

The kubevirt-iso builder now registers build artifacts with the HCP Packer
registry after each successful build. When a hcp_packer_registry block is
present in the template, Packer core will track the resulting DataSource
as a versioned artifact in the registry.

artifact.go

• Added Namespace and StateData fields to Artifact
• Id() now returns namespace/name (e.g. images/fedora-42) so HCP can
  track artifacts unambiguously across clusters
• State() handles the registryimage.ArtifactStateURI key
  ("par.artifact.metadata") and returns a populated *registryimage.Image
  with provider=kubevirt, region=<namespace>, and labels including
  namespace and any values from generated_data

builder.go

• Prepare() returns []string{"BootableVolumeName"} so provisioners can
  reference the artifact name at runtime via build.BootableVolumeName
• Run() wires packerbuilderdata.GeneratedData so generated values are
  accessible in provisioner interpolation
• Added post-runner state.GetOk("error") and state.GetOk(StateCancelled)
  checks before artifact construction — previously a halted build would return
  a misleading "bootable volume name not found in state" error instead of
  the real underlying error
• StepCreateBootableVolume is gated on !SkipCreateImage so the step is
  skipped when the flag is set

config.go

• Added skip_create_image bool — when true, skips the final
  StepCreateBootableVolume step and returns no artifact, which also
  suppresses HCP registration. Useful for iterative debugging without
  producing a final image.

step_create_bootablevolume.go

• Added GeneratedData *packerbuilderdata.GeneratedData field
• Calls GeneratedData.Put("BootableVolumeName", ds.Name) so the value is
  available to provisioners
• Stores bootable_volume_namespace in the state bag alongside the existing
  bootable_volume_name so Builder.Run() can construct a fully-qualified
  artifact ID

artifact_test.go (new)

• Table-driven unit tests covering BuilderId, Id, String, Files,
  Destroy, State(ArtifactStateURI) with and without generated_data,
  and StateData fallthrough including nil map safety

step_create_bootablevolume_test.go

• Wired GeneratedData into BeforeEach to prevent nil pointer panic

---

2. CD-ROM bus type — intermediate fix (cde2306)

During testing, KubeVirt's admission webhook rejected the VM because Linux
CD-ROM devices had no Bus set. KubeVirt was defaulting to virtio, which
is an invalid bus type for CD-ROM devices. This commit hardcoded sata as
a stepping stone; it was immediately superseded by commit ef8f80d.

---

3. Configurable CD-ROM bus type (ef8f80d)

The intermediate sata fix broke arm64 clusters (including OpenShift on
ARM), where the admission webhook only accepts virtio or scsi for disk
buses. Rather than hardcode either value, this commit exposes disk_bus as
a user-configurable field.

config.go

• Added disk_bus string field with mapstructure:"disk_bus"
• Prepare() defaults to "scsi" when unset — valid on both x86 and arm64

resources.go

• getLinuxVirtualMachineDisks() now accepts diskBus string and applies
  v1.DiskBus(diskBus) to both the cdrom and oemdrv CD-ROM devices
• Windows VM disks are unaffected (already explicitly set to sata)

step_create_virtualmachine.go

• Reads s.Config.DiskBus and passes it through to virtualMachine()

Example usage in template:

source "kubevirt-iso" "example" {
  disk_bus = "scsi"   # arm64 clusters
  # disk_bus = "sata" # x86 clusters if needed
}

---

What was tested

All existing unit tests pass. New unit tests for the HCP artifact wiring pass.

ok  github.com/hashicorp/packer-plugin-kubevirt/builder/kubevirt/iso  5.3s

End-to-end testing was carried out on a local minikube cluster (qemu2 driver,
Apple Silicon). The following was verified locally:

• packer validate accepts hcp_packer_registry {} and skip_create_image
• HCP credentials authenticate correctly (Tracking build on HCP Packer with fingerprint ... appears in build output)
• StepValidateIsoDataVolume reaches the cluster and validates the ISO
  DataVolume successfully
• StepCopyMediaFiles creates the ConfigMap successfully
• StepCreateVirtualMachine creates the VM with disk_bus = "scsi" without
  rejection from the admission webhook

End-to-end VM boot and full HCP artifact registration could not be completed
locally due to a minikube + Docker networking constraint (nf_nat table
operations are not permitted inside a Docker container, which prevents
KubeVirt's masquerade networking from initialising the VM's network stack).
This is an environment limitation, not a plugin issue.

Remaining tests required before merge

The following must be run on a Linux-based KubeVirt cluster (bare metal,
OpenShift Local/CRC, or a cloud-hosted cluster):

1. Full build completes and registers with HCP

packer build hcp-test.pkr.hcl

Expected:

• Build runs to completion
• Terminal output contains:

  kubevirt-iso.test: Bootable volume: images/hcp-test-image
  

• HCP portal → Packer → Buckets → kubevirt-test → latest version shows:

Field	Expected
Artifact ID	images/hcp-test-image
Provider	kubevirt
Region	images
Label: namespace	images
Label: BootableVolumeName	hcp-test-image

2. build.BootableVolumeName is accessible in provisioners

Add to the build block:

provisioner "shell" {
  inline = ["echo BootableVolumeName=${build.BootableVolumeName}"]
}

Expected: Provisioner output contains BootableVolumeName=hcp-test-image
and not the ERR_* placeholder.

3. Second build creates a new version

Change name to hcp-test-image-2 and re-run.

Expected: HCP bucket shows 2 distinct versions.

4. Failed build is not registered

Set iso_volume_name to a DataVolume that does not exist and run.

Expected: Build exits non-zero, no new version in HCP bucket.

5. skip_create_image = true suppresses HCP registration

Add skip_create_image = true to the source block and run.

Expected: No Creating a new bootable volume log line, no artifact
output, no new version in HCP bucket.

[hashicorp-cla-app]

All committers have signed the CLA.

[dejo-oyelese]

Hi @anurag5sh - sorry I duplicated PRs but I closed the other one. I fixed the tests and this should be good to go now.