Fix cross-process UEFI snapshot restore + Windows save fsync, add regression test

[ayusharora221204]

Summary

Fixes two bugs surfaced by cross-process snapshot restore (openvmm --restore-snapshot into a fresh worker process), and adds a petri integration test that gates the UEFI regression.

Bug 1 — Windows save fsync

handle_save_snapshot fsynced the memory backing file via a read-only handle. On Windows sync_all maps to FlushFileBuffers, which requires a handle opened with write access, so save failed with Access is denied (os error 5). Fix: open the file writable before sync_all. Adds mock unit tests documenting the bug.

Bug 2 — UEFI restore resolver

Restore forces load_mode = None, so the UEFI platform resolvers were never registered, and restoring a UEFI snapshot onto a fresh worker panicked with no resolver for uefi_logger:platform. Fix: detect a restored UEFI VM from the saved state's "uefi" state unit and register the resolvers in that case too.

Test + plumbing

• New uefi_cross_process_restore (gated unstable, Alpine UEFI x64): boots a worker, saves, tears it down, then restores the snapshot on a fresh worker — the only path that reproduces Bug 2 (the in-process pulse restores into the same worker and can't hit it).
• Worker::launch takes an optional saved_state; run_restore forces load_mode = None and skips the in-process pulse; save_state_protobuf; Clone on the PetriVmConfig recipe (incl. a manual Clone for BootImageConfig<T>).

Testing

• Runtime-validated on KVM (WSL2): PASS uefi_cross_process_restore.
• Negative control: with the Bug 2 fix removed, the test FAILS with no resolver for uefi_logger:platform, confirming it gates the regression.
• rustfmt --check clean; mock unit tests for Bug 1 pass.

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[Copilot]

Pull request overview

Fixes snapshot save/restore correctness across two critical scenarios: Windows snapshot save (fsync) and cross-process UEFI snapshot restore into a fresh worker (mirroring openvmm --restore-snapshot). It also adds a Petri integration regression test to ensure the UEFI resolver registration bug can’t regress.

Changes:

• Fix Windows snapshot save by opening the memory backing file with write access before sync_all.
• Fix cross-process UEFI snapshot restore by registering UEFI platform resolvers when restored state indicates a UEFI VM (even when load_mode = None).
• Add Petri cross-process restore plumbing + a new unstable integration test that reproduces the previously-missed restore path.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
vmm_tests/vmm_tests/tests/tests/multiarch/save_restore.rs	Adds an unstable Petri integration test for cross-process UEFI snapshot restore.
vmm_tests/vmm_tests/tests/tests/multiarch.rs	Wires the new save_restore test module into the multiarch suite.
petri/src/worker.rs	Extends Worker::launch to accept an optional saved-state payload.
petri/src/vm/openvmm/start.rs	Adds a “restore on fresh worker” startup path and skips in-process save/restore pulse during restore.
petri/src/vm/openvmm/runtime.rs	Exposes a raw ProtobufMessage save-state API to avoid encode/decode roundtrips.
petri/src/vm/openvmm/mod.rs	Implements PetriVmBuilder::verify_openvmm_cross_process_restore helper used by the new test.
petri/src/vm/mod.rs	Enables cloning of VM recipe/config types needed to launch two identical workers.
openvmm/openvmm_helpers/src/snapshot.rs	Adds unit tests documenting the Windows sync_all read-only-handle failure and the fixed behavior.
openvmm/openvmm_entry/src/vm_controller.rs	Fixes the Windows fsync bug by opening the memory backing file writable before sync_all.
openvmm/openvmm_core/src/worker/dispatch.rs	Detects restored UEFI state from saved state and registers UEFI platform resolvers accordingly.

[github-actions]

34 Petri tests failed (5 unstable)

[Steven Malis (smalis-msft)]

Maybe we want to have a new LoadMode::Restore or something along those lines...