[nanvix] Add Linux/KVM Support

[ppenna]

📖 Description

Extends the Nanvix MicroVM containment backend to Linux via KVM, mirroring the existing Windows/WHP implementation, and adds a Linux E2E test suite to cover it.

Runtime (wxc_common/src/nanvix_runner.rs)

• Split runner internals along target_os: Windows keeps the WHP snapshot warm-start; Linux cold-boots the VM via KVM on every invocation (no snapshot, no -snapshot/-bin-dir args; cwd set to exe dir).
• Generalize the watchdog: usize carries a duplicated process HANDLE on Windows and the child PID on Linux; on timeout, Linux delivers SIGKILL via libc::kill instead of TerminateProcess.
• Gate snapshot resolution, NANVIX_HOME, DEFAULT_HOME_LEAF, and SNAPSHOT_CBOR behind cfg(target_os = "windows").
• Use nanvix_common::NANVIXD_BINARY for the platform-correct daemon name (nanvixd.exe / nanvixd.elf).
• New unit tests: signal-killed copyback skip, platform constant check, total-timeout sentinel/overflow, NanVixError display variants.

Staging (wxc_common/src/microvm_staging.rs)

• Fix host_path_to_guest_relative to strip leading slashes so Linux absolute paths (/tmp/xyz) become guest-relative (tmp/xyz).
• Update existing rewrite test for the Linux case where the host path is a substring of the guest path; add two new tests covering leading-slash stripping.

lxc binary (src/lxc)

• Add microvm cargo feature that enables wxc_common/microvm and depends on nanvix_binaries so KVM artifacts are downloaded/staged.
• New build.rs copies staged Nanvix artifacts next to lxc-exec using nanvix_common::copy_artifacts_to_target and DEP_NANVIX_BINARIES_BIN_DIR.
• Wire ContainmentBackend::MicroVm in main.rs: gated by --experimental, returns NanVixScriptRunner when compiled with microvm, otherwise exits with a clear error.

nanvix_binaries (src/nanvix_binaries)

• Build script now handles target_os = "linux" in addition to Windows: downloads microvm-standalone-256mb.tar.gz, extracts flat binaries from <prefix>/ and kernel files from <prefix>/bin/ via tar --strip-components, and verifies SHA256 sums via sha256sum. Snapshot pre-generation remains Windows-only.
• versions.json: bump tag to 3.12.3-nanvix-0.15.19-9558cff and add asset_linux / binaries_linux fields.
• checksums.json: restructured into per-platform { "windows": .., "linux": .. } sub-maps with new hashes for both targets.

nanvix_common (src/nanvix_common)

• REQUIRED_BINARIES and new NANVIXD_BINARY are cfg-gated per target_os so both daemons can be referenced symbolically.
• RepoConfig gains optional asset_linux / binaries_linux fields (serde default).
• load_checksums accepts either the legacy flat map or the new platform-keyed form, selected by a platform: &str argument.

wxc_common (Cargo.toml + lib.rs)

• Move nanvix_common and uuid out of the Windows-only target section so the microvm feature works on Linux; add a Linux-only libc dep used by the watchdog SIGKILL path.
• Drop the target_os = "windows" gate from microvm_staging and nanvix_runner module declarations (the runner now compiles on Linux too).

Build & docs

• build.sh: add --with-microvm flag, composed with --with-hyperlight via a FEATURES_LIST array.
• docs/nanvix-microvm/nanvix.md: document Linux prerequisites (/dev/kvm, lxc-exec, --with-microvm) and note that warm-start via snapshots is Windows-only.

E2E tests (tests/e2e_linux_microvm.rs + test_configs/microvm_*_linux.json)

• Mirrors the Windows MicroVM E2E suite, invoking lxc-exec directly with containment=microvm.
• Adds skip guards (has_lxc_exe, has_lxc_nanvix_binaries, has_kvm), a full-suite test with per-case timing emitted to microvm-perf-results-linux.json, and an #[ignore] repeat-stress test.
• Adds 7 new test_configs/microvm_*_linux.json covering hello, exit code, multiline, stdlib, large output, exception, and timeout cases.

No schema or SDK changes — backend selection still uses "containment": "microvm".

🔗 References

None.

🔍 Validation

• cargo build --release -p lxc --features microvm on Linux x86_64.
• cargo test -p wxc_common — new unit tests for the watchdog signal-kill skip, platform constants, timeout sentinel/overflow, NanVixError display, and the staging leading-slash stripping all pass.
• cargo test -p wxc_e2e_tests --test e2e_linux_microvm against a host with /dev/kvm and a built lxc-exec — all 7 cases pass and microvm-perf-results-linux.json is emitted.
• Existing Windows MicroVM path unchanged; Windows behavior verified to still cold-resolve snapshot + warm-start via WHP.

✅ Checklist

• Signed the Contributor License Agreement
• Linked to an issue
• Updated documentation (if applicable)
• Updated Copilot instructions (if build, architecture, or conventions changed)

📋 Issue Type

• Bug fix
• Feature
• Task

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

Adds Linux/KVM support for the NanVix MicroVM backend, aligning the Rust runtime and build/staging pipeline with the existing Windows/WHP implementation, and introduces a Linux-focused E2E test suite plus new test configs.

Changes:

• Extends NanVixScriptRunner and staging logic to compile/run on Linux (cold-boot via KVM; Windows keeps snapshot warm-start).
• Adds Linux E2E tests that invoke lxc-exec with containment=microvm, along with new Linux microvm test_configs/.
• Updates build + binary acquisition to support Linux NanVix artifacts (new versions/checksums layout) and adds a --with-microvm option to build.sh.

Show a summary per file

File	Description
test_configs/microvm_hello_linux.json	New Linux MicroVM “hello” config.
test_configs/microvm_exit_code_linux.json	New Linux MicroVM exit-code propagation config.
test_configs/microvm_multiline_linux.json	New Linux MicroVM multi-line script config.
test_configs/microvm_stdlib_linux.json	New Linux MicroVM stdlib import/use config.
test_configs/microvm_large_output_linux.json	New Linux MicroVM large-output config.
test_configs/microvm_error_linux.json	New Linux MicroVM exception config.
test_configs/microvm_timeout_linux.json	New Linux MicroVM timeout config.
src/wxc_e2e_tests/tests/e2e_linux_microvm.rs	Adds a Linux MicroVM E2E suite + perf output + stress test.
src/wxc_e2e_tests/src/lib.rs	Adds Linux target triples and helpers to locate/run lxc-exec + prerequisites (/dev/kvm, staged NanVix binaries).
src/wxc_common/src/nanvix_runner.rs	Splits Windows vs Linux runner behavior; Linux KVM cold-boot; Linux watchdog uses SIGKILL. Adds unit tests.
src/wxc_common/src/microvm_staging.rs	Fixes Linux absolute-path handling by stripping leading slashes; updates/adds tests.
src/wxc_common/src/lib.rs	Builds microvm modules when feature="microvm" is enabled (now not Windows-only).
src/wxc_common/Cargo.toml	Moves microvm deps out of Windows-only section; adds Linux-only libc dep.
src/nanvix_common/src/lib.rs	Adds platform-conditional REQUIRED_BINARIES + NANVIXD_BINARY; extends repo config for Linux; updates checksum loader to accept platform-keyed format.
src/nanvix_binaries/versions.json	Bumps pinned tag; adds Linux asset/binaries fields.
src/nanvix_binaries/checksums.json	Restructures checksums into { windows: {...}, linux: {...} } with updated hashes.
src/nanvix_binaries/build.rs	Adds Linux download/extract/verify flow for tar.gz assets; retains Windows snapshot pre-generation behavior.
src/lxc/src/main.rs	Wires ContainmentBackend::MicroVm for lxc-exec behind --experimental and the microvm feature.
src/lxc/Cargo.toml	Adds microvm feature (pulls in wxc_common/microvm + nanvix_binaries) and a build-dependency on nanvix_common.
src/lxc/build.rs	Copies staged NanVix artifacts next to the built lxc-exec when microvm is enabled.
src/Cargo.lock	Updates dependency graph for new feature/deps.
docs/nanvix-microvm/nanvix.md	Documents Linux/KVM prerequisites and clarifies Windows-only snapshot warm-start.
build.sh	Adds --with-microvm and composes features with --with-hyperlight.

Copilot's findings

Comments suppressed due to low confidence (1)

src/wxc_common/Cargo.toml:48

• On Linux, libc is only used by the MicroVM watchdog path (nanvix_runner), but it is currently an unconditional dependency for all Linux builds of wxc_common. Making it an optional dependency enabled by the microvm feature would avoid pulling libc into non-microvm builds.

[target.'cfg(target_os = "linux")'.dependencies]
libc = { workspace = true }

• Files reviewed: 22/23 changed files
• Comments generated: 3

[bbonaby]

closing and reopening to see if that updates the ADO status syncing

[huzaifa-d]

/azp run

[azure-pipelines]

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