Repin OpenVMM to microVM v2.1

[Pedro Henrique Penna (ppenna)]

Repin OpenVMM to microVM v2.1

This PR pins the openvmm submodule to eb32b165271d9a12773ae4333377549cb0cc7f71,
the head of the new nanvix/openvmm microvm/v2.1 branch. It also changes the
branch that .gitmodules tracks from main to microvm/v2.1. Those two paths
are the only changes.

• OpenVMM review PR: microVM v2.1: rebase the microVM stack onto microsoft/openvmm main nanvix/openvmm#102 (microvm/v2.1 → upstream/main)
• Previous pin: e2c982abc (Restore listener endpoint rebinding nanvix/openvmm#99 on top of nanvix/openvmm main 5cfdf9220)
• New pin: eb32b1652, which is 5cfdf9220's 161-commit microVM stack rebased
  onto microsoft/openvmm main at e1cdbd916, plus e2c982abc. nanvix/openvmm
  upstream/main now mirrors e1cdbd916.
• Head submitted to CI: 023f5c6ebb754cf3d0f0f50ffc17e6f8934df4d1, directly on dev 220b4f4

Equivalence

git range-diff e7de393fe..e2c982abc e1cdbd916..eb32b1652 reports 139 unchanged
commits and 23 changed commits. No commit was added, dropped, or reordered. The
changed commits carry conflict resolutions against 27 upstream commits and
adaptations to upstream API changes. The review PR lists each one. The tree
differs from the previous pin by the upstream changes and those adaptations, so
this is a behavioral promotion, not a tree-identical one.

One change is visible to management clients. Upstream assigns the new
VMConfig.disable_vmbus and disable_hv flags to protobuf fields 16 and 17, but
NVX clients already use those fields for crash_dump_path and machine_profile.
The fork therefore moves the two flags to fields 20 and 21 and keeps every
existing NVX tag.

Validation

Validation ran on bare-metal hosts, in isolated checkouts, with guest artifacts
built with Docker from these sources. The OpenVMM correctness and benchmark runs
used NVX 52c9a0bb6. That commit makes the same two-path change on the previous
dev tip 5edac1c. The newer dev commits change only performance baselines,
doc/usage.md, and sandbox network-list validation, and none of them affects
OpenVMM or guest inputs. At this PR head, NVX verify, the CLI tests, and the
Ubuntu sandbox smoke test were rerun on all three hosts.

Check	Linux/KVM	Linux/MSHV	Windows/WHP
test-microvm, Alpine (every scenario; 1/2/4/8 vCPU)	pass	pass	pass
Ubuntu smoke and sandbox smoke	pass	pass	pass
Ubuntu extended (KVM only)	pass	n/a	n/a
test-openvmm	58/58	57/57	29/29
test-openvmm-unit	4535 passed, 82 doc tests	4535 passed, 82 doc tests	4235 passed, 82 doc tests
CI-equivalent benchmark (34 one-vCPU metrics and multi-vCPU restore)	pass	pass	pass

• A same-host benchmark A/B against e2c982abc found no regression beyond
  run-to-run noise. On MSHV, the collector rejected the first run of each revision,
  which started right after a build, for unstable snapshot generation. The reruns
  on the idle host passed. On WHP, the v2.1 acceptance run needed the single CI
  retry for the same check.
• OpenVMM clippy with Rust 1.95.0 is clean across the workspace on Linux and
  Windows, and cargo xtask fmt passes. All 162 commits of microvm/v2.1 pass cargo check --workspace --all-targets with Rust 1.95.0 on both Linux and Windows.
• NVX ruff, ruff format, pyright for both platforms, shellcheck, shfmt, the Specula
  tests, and the PowerShell syntax check pass.
• The bare-metal KVM host has a 98 GB disk, so its unit-test build used
  CARGO_PROFILE_DEV_DEBUG=line-tables-only and CARGO_INCREMENTAL=0. The MSHV
  and WHP hosts used the default profile.
• CI run 36539477824
  passed on attempt 2 at this head. Attempt 1 passed every job except the Linux/MSHV
  virtual-machine platform benchmark. That job's collector rejected acceptance
  samples as unstable snapshot generation (p50 25.9% above p25, limit 25%). The
  rerun of the failed jobs passed, and the performance regression gate passed all
  111 checks.

[Copilot]

Copilot review overview

🔵 Needs a closer look

The pin imports a 162-commit behavioral promotion whose source review and exact-head CI remain incomplete.

Review effort: Balanced
Findings: None

What changed in this PR

Repins NVX to the OpenVMM microVM v2.1 stack and tracks its release branch.

Changes:

• Updates the OpenVMM gitlink to eb32b1652.
• Changes submodule tracking from main to microvm/v2.1.

File	Description
.gitmodules	Tracks the microVM v2.1 branch.
openvmm	Pins the corresponding OpenVMM revision.

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[Copilot]

Copilot review overview

🟡 Changes recommended

The current pin lacks matching provenance and completed exact-head validation.

Review effort: Balanced
Findings: None

[Copilot]

Copilot review overview

🟡 Changes recommended

The submodule still tracks main, and validation evidence does not cover the newly rewritten OpenVMM head.

Review effort: Balanced
Findings: None