QEMU Build

Audit workflow

For a non-trivial task that writes to the workspace, use only the needed entries under .oh-my-qemu/<task-slug>/: audit.md (baseline, plan, decisions, evidence, verification, and gaps), commands.md (redacted commands, working directories, and results), logs/ (decisive build, test, and runtime output), scripts/ (probes, parsers, and harnesses), and output/ (generated deliverables, third-party dependencies, and non-QEMU binaries). Keep QEMU's own build tree at source-root builds/build-<target>/, never an unqualified build/. In a Git worktree, add .agents/, .oh-my-qemu/, and builds/ to the file from git rev-parse --git-path info/exclude before writing artifacts or configuring QEMU; preserve existing entries and avoid duplicates. Never stage or commit these paths; stage source only when the user explicitly requests that separate action. At handoff, reconcile git status --short with the baseline and report the task directory, build directory, source changes, pre-existing changes, and unresolved gaps.

QEMU upstream boundary

QEMU's official GitLab and mailing lists are upstream channels. A patch becomes an upstream contribution when it is sent to the maintainers selected through MAINTAINERS. Do not prepare or send agent-generated code, documentation, commit messages, or patches for upstream submission; see the checked-out tree's docs/devel/code-provenance.rst. Research, debugging, analysis, local experiments, verification, and workflow guidance remain allowed. Local branches, commits, patch files, pushes, and pull requests are not by themselves upstream contributions; perform those Git actions only when requested.

Scope boundary

This skill configures and builds the QEMU source tree only. Use qemu-kernel-build for Linux kernel artifacts and qemu-uboot-build for U-Boot and firmware-stage artifacts. One named build directory per component; one skill per build class.

Build directory rule

Use a descriptive directory under source-root builds/ for every configuration, such as builds/build-aarch64/ or builds/build-riscv64-debug/. Never configure QEMU in build/, the source root, or the task output/ directory. Reuse a directory only when its recorded configuration matches the task.

Inspect before creating or reconfiguring: config.log for the configure command and source path; build.ninja for configured state; pyvenv/bin/meson for Meson commands; meson-logs/meson-log.txt for configure failures. If config.log names a different source root, prefix, or toolchain, the directory is stale: create a new named directory instead.

Environment preflight

Record absolute paths and versions before the first build; do not rely on an interactive shell. Run scripts/preflight.sh first, or see references/host-matrix.md for host notes and failures.

• command -v ninja meson python3 pkg-config cc and each resolved path plus version.
• The build directory's pyvenv/bin/meson and the configured Ninja when PATH lacks them.
• A readable and writable HOME for the executing user; a Meson reconfigure can fail when HOME belongs to another user.
• Compiler, sysroot, and pkg-config paths recorded in config.log.
• Host runtime libraries needed to run the built QEMU; if missing, build and run in the documented container and record both environments.

Concurrency

Run one configure step and one Ninja invocation per build directory at a time. Do not share a build directory between concurrent agents or tasks. If a build is already running, inspect its process and log, then wait or use a separate named build directory.

Configure

From the QEMU source root:

mkdir -p builds/build-aarch64
cd builds/build-aarch64
../../configure --target-list=aarch64-softmmu

Use ../../configure --help in the build directory for options supported by the checked-out version. Typical options are --enable-debug, --enable-trace-backends=log, and --enable-asan or --enable-ubsan or --enable-tsan. Reconfigure from config.log, changing only the needed option; keep the target list and diagnostic options unless the task changes them.

Record any deviation, for example --disable-werror with the warning text that forced it. Do not disable warnings silently, and for generated-source failures fix the generator input rather than files under builds/build-<target>/.

Build

From the source root, build the whole configuration or prefer narrow targets:

ninja -C builds/build-aarch64
ninja -C builds/build-riscv64 qemu-system-riscv64 tests/qtest/<test-name>

Use -v only for diagnosis.

Pre-compile checklist

Before a long build after source edits: confirm edited headers are included; confirm called QEMU APIs and struct fields exist in the checked-out tree; confirm feature guards match configured targets and options; confirm new sources and qtests are registered in Meson; confirm changed public signatures have all call sites updated.

Canonical gate

For a change or a build claim, record these results before reporting PASS: the narrow build of the affected target from a named build directory; the matching qtest or focused verification; scripts/checkpatch.pl when source patches exist; git diff --check and reconciliation of git status --short. Record the build in assets/build-record-template.md; report every skipped gate as an unresolved gap.

Failure classification

• Configure: missing dependency, unsupported option, Python/Meson issue, compiler mismatch, unreadable HOME, or stale build directory.
• Compile: API/type/include/feature-guard mismatch; check the checked-out headers and nearby maintained code.
• Link: missing object in Meson, missing dependency, target-specific source not linked.
• Generated source: QAPI, trace-events, decodetree, or another Meson generator input.
• Toolchain/host: sanitizer or compiler incompatibility, missing host library.

When background or sub-agent execution is unavailable, run the build as a bounded foreground command, keep the full log under task logs/, and report the exit status and failure excerpt instead of claiming completion.

Upstream references

• docs/devel/build-system.rst
• docs/devel/testing/main.rst
• docs/devel/submitting-a-patch.rst
• docs/devel/code-provenance.rst

Paths can differ between QEMU versions; locate them in the checked-out tree.