s390x/zipl: clear LOADDEV before setting it

[nikita-dubrovskii]

If several disks are attached to zVM, more than one may have been used as LOADDEV, which would cause an error like:

  HCPFCL1613E An attempt was made to set both SCSI and ECKD parameters
  for a future IPL. These are conflicting parameters.

[coderabbitai]

📝 Walkthrough

Walkthrough

Changes

The s390x LOADDEV setup now clears existing configuration before setting a new device. Clear failures are logged and ignored. The release notes document the fix.

s390x LOADDEV reset

Layer / File(s)	Summary
Clear LOADDEV before configuration src/s390x/zipl.rs, docs/release-notes.md	set_loaddev clears existing LOADDEV parameters before configuring the new device. Clear errors are logged without aborting. The 0.27.0 release notes document the change.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: dustymabe

Merge Risk: 🟡 Moderate · up to 57394

A failed device inspection during secure installation can now leave a z/VM guest without its previous LOADDEV configuration. Validate the replacement before clearing the existing configuration.

🚥 Pre-merge checks | ✅ 7

✅ Passed checks (7 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title follows the required format. It uses the s390x/zipl subsystem, an imperative lowercase description, and no trailing period.
Description check	✅ Passed	The description explains the LOADDEV conflict on z/VM and the resulting HCPFCL1613E error. It directly relates to the changeset.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files. (1 skipped: 1 …
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Commit Message Convention	✅ Passed	The PR contains one non-merge commit: s390x/zipl: clear LOADDEV before setting it. The subsystem is valid, the description starts with the lowercase imperative clear, and the subject has no traili…
Release Notes	✅ Passed	The pull request changes LOADDEV behavior in src/s390x/zipl.rs by clearing LOADDEV before setting it. It also updates docs/release-notes.md under Internal changes with a bullet that describes this…

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Actionable comments posted: 1

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Inline comments:
In `@src/s390x/zipl.rs`:
- Line 122: Update set_loaddev to call parse_lszdev(dev) before executing the
vmcp SET LOADDEV CLEAR command, propagate any parse error without clearing the
existing configuration, and reuse the parsed value for subsequent setup instead
of parsing again.

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Architecture-specific code for IBM Z.

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🔇 Additional comments (1)

docs/release-notes.md (1)

28-28: LGTM!

[nikita-dubrovskii]

Putting this on hold, as zVM may crash.