compute: add PCI topology and hotplug port reservation docs

[mhenriks]

Document the PCI topology versions (v1, v2, v3), how hotplug port reservation works, and upgrade behavior. Includes troubleshooting guidance for Windows VMs with offline disks after upgrading from KubeVirt 1.6/1.7 to versions with the v3 fix (1.6.4, 1.7.2, 1.8+).

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

Checklist

This checklist is not enforcing, but it's a reminder of items that could be relevant to every PR.
Approvers are expected to review this list.

• Design: A design document was considered and is present (link) or not required
• PR: The PR description is expressive enough and will help future contributors
• Code: Write code that humans can understand and Keep it simple
• Refactor: You have left the code cleaner than you found it (Boy Scout Rule)
• Upgrade: Impact of this change on upgrade flows was considered and addressed if required
• Testing: New code requires new unit tests. New features and bug fixes require at least on e2e test
• Documentation: A user-guide update was considered and is present (link) or not required. You want a user-guide update if it's a user facing feature / API change.
• Community: Announcement to kubevirt-dev was considered

Release note:

compute: add PCI topology and hotplug port reservation docs

[mhenriks]

cc @jean-edouard @vladikr @xpivarc

[kubevirt-bot]

There has been no activity on this PR for 45 days.
To protect limited CI resources, it has been automatically labelled 'stale'.
This PR will automatically rot after an additional 14 days of inactivity, and will be closed shortly after that.

What you can do:

• If the PR is waiting on you to respond to a question or feedback and/or update the PR, please do so.
• You can mark the PR as fresh and remove the label with the following command: /remove-lifecycle stale
• If this PR is safe to close now, please help the project by closing it with: /close
• If you need attention on this PR from a reviewer, you can raise it on the agenda of the relevant SIG meeting or KubeVirt Community meeting, or ping the kubevirt-dev slack channel.

/lifecycle stale

[mhenriks]

/remove-lifecycle stale

[kubevirt-bot]

PR needs rebase.

Details

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[jean-edouard]

/approve

[kubevirt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jean-edouard

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Details

Needs approval from an approver in each of these files:

• docs/compute/OWNERS [jean-edouard]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[dhiller]

Removing needs-rebase label — the PR was force-pushed after the label was applied, which likely coincided with a GitHub glitch.

🤖 Assisted by Claude

[aburdenthehand]

Nice work @mhenriks
For the most part this is clean and clear but I think the Topology:KubeVirt versioning could be made clearer, along with a lot of the headings.

[aburdenthehand]

We previously said "Understanding these is important when upgrading, as VMs created under different versions may behave differently."
So let's add an introduction here that more or less repeats that and links back to the Topology–KubeVirt version table. We can also then simplify these headings so they don't need the KubeVirt versions in them. (ie ### Upgrading from v1 to v3)