Re: [RFC PATCH 05/10] .agents/skills: add qemu-build skill

["Alex Bennée" <alex.bennee@linaro.org>]

Alejandro Jimenez <alejandro.j.jimenez@oracle.com> writes:

> On 5/5/26 1:01 PM, Alex Bennée wrote:
>> This provides basic instructions for building QEMU.
>> 
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> ---
>>  .agents/skills/qemu-build/SKILL.md | 50 ++++++++++++++++++++++++++++++
>>  1 file changed, 50 insertions(+)
>>  create mode 100644 .agents/skills/qemu-build/SKILL.md
>> 
>> diff --git a/.agents/skills/qemu-build/SKILL.md b/.agents/skills/qemu-build/SKILL.md
>> new file mode 100644
>> index 00000000000..a78678ff632
>> --- /dev/null
>> +++ b/.agents/skills/qemu-build/SKILL.md
>> @@ -0,0 +1,50 @@
>> +---
>> +name: qemu-build
>> +description: Provides step-by-step instructions on configuring and
>> building QEMU. You MUST trigger this skill whenever the user asks to
>> build QEMU or debug build failures. It includes critical details on
>> build directory reuse and spawning sub-agents.
>> +license: GPL-2.0-or-later
>> +---
>> +
>> +# Instructions
>> +
>> +## Examining and Re-using Build Directories
>> +Before creating a new build directory, check if an existing one can be re-used. QEMU uses out-of-tree builds, typically in `build` or `builds/` sub-directories.
>> +
>> +1. **Check existing configs**: You can examine how an existing
>> build directory was configured by checking its `config.log`. Run
>> `head -n 2 builds/<dir>/config.log`. The second line typically
>> contains the full `../configure` command line used.
>> +2. **Re-use and Reconfigure**: You have latitude to re-use existing
>> directories when appropriate (e.g., `builds/debug` which is a
>> general-purpose debug directory for whatever is currently going on).
>> If an existing directory has the right flags (like debug/sanitizers)
>> but the wrong target list, you can reconfigure it to keep the same
>> config but change the `--target-list`:
>> +   ```bash
>> +   cd builds/debug
>> +   # Check the old config.log, then re-run configure with the new target-list
>> +   ../../configure <old-flags> --target-list=<new-targets>
>> +   ```
>> +
>> +## Launching Builds
>> +**Crucial**: You MUST NEVER run builds directly in the main agent context. You MUST ALWAYS launch them by spawning a sub-agent using the `eca__spawn_agent` tool.
>
> "ECA heritage" showing with the eca__spawn_agent mention. Ending the
> sentence after "sub-agent" is likely enough for the model to do the right
> thing based on its available tools?
>
>> +Always use the `qemu-helper-agent` for these tasks.

And this is on my personal config as well ;-)

I have added a rule to my config:

  ---
  paths: 
    - "/home/alex/lsrc/qemu.git/**"
  ---

  There is a qemu-helper-agent for use in QEMU related tasks.
  Use `env GITLAB_TOKEN=$(pass gitlab-api)` to pass the auth token for glab actions.

And cleaned up the references from the project agent skills.

>> +Pass the specific build commands, along with the required working directory, in the `task` argument. Give the subagent explicit instructions on what to verify and what to report back to you.
>> +For example: `task: "Navigate to builds/debug and run ninja. If it fails, report the exact compiler errors."`
>> +
>> +## Configuring a New Build
>> +If no suitable build directory exists, create a new one.
>> +
>> +1. **Create build directory**: `mkdir -p builds/test-target; cd builds/test-target`
>> +2. **Basic Configure**: `../../configure --target-list=[list of targets]`
>> +   - Common targets: `x86_64-softmmu`, `aarch64-softmmu`, `riscv64-softmmu`, `x86_64-linux-user`.
>> +3. **Common Options**:
>> +   - `--enable-debug-info`: Include symbols.
>> +   - `--enable-debug`: Enable assertions.
>> +4. **Sanitizers**:
>> +   - `--enable-asan`: Address Sanitizer.
>> +   - `--enable-tsan`: Thread Sanitizer.
>> +   - `--enable-ubsan`: Undefined Behavior Sanitizer.
>> +
>> +## Building
>> +**Important**: Always re-run the build after making changes to the source code.
>> +
>> +## Reporting Results
>> +**Crucial**: After completing the build task, provide a concise summary of the results to the calling agent.
>> +1. **Summary**: State whether the build passed or failed.
>> +2. **Failure Excerpts**: If the build fails, include relevant excerpts from the logs (e.g., compiler errors).
>> +3. **Full Paths**: Always provide the **absolute file paths** to the full logs for further inspection.
>> +
>> +## Debugging and Environment
>> +- **Verbose**: `V=1` for detailed output.

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro