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Contributing to Jailhouse

Contributions to Jailhouse are always welcome. This document explains the general requirements on contributions and the recommended preparation steps. It also sketches the typical integration process of patches.

Contribution Checklist

  • use git to manage your changes [recomended]

  • follow Documentation/coding-style.txt coding style [required]

    • for python code run pep8 coding style checker [required]
  • add the required copyright header to each new file introduced, see licensing information [required]

  • structure patches logically, in small steps [required]

    • one separable functionality/fix/refactoring = one patch
    • do not mix those there in a single patch
    • after each patch, the tree still has to build and work, i.e. do not add even temporary breakages inside a patch series (helps when tracking down bugs)
    • use git rebase -i to restructure a patch series
  • base patches on top of latest master or - if there are dependencies - on next (note: next is an integration branch that may change non-linearly)

  • test patches sufficiently (obvious, but...) [required]

    • no regressions are caused in affected code
    • seemingly unaffected architectures still build (use Travis CI e.g.)
    • static code analyzer finds no new defects (register a github fork with Travis CI and Coverity for free scanning) [recommended]
    • python code shall be tested with python 2 and 3 [required]
    • the world is still spinning
  • add signed-off to all patches [required]

    • to certify the "Developer's Certificate of Origin", see below
    • check with your employer when not working on your own!
  • add Fixes: to all bug-fix commits [recommended]

    • the Fixes: tag format shall be: Fixes: 12-byte-hash ("subject of bug-introducting commit")
    • if you are unsure of the bug-introducting commit do not add a Fixes: tag - no Fixes: tag is better than a wrong Fixes: tag.
  • post patches to mailing list [required]

    • use git format-patch/send-email if possible
    • send patches inline, do not append them
    • no HTML emails!
    • CC people who you think should look at the patches, e.g.
      • affected maintainers (see areas of responsibility below)
      • someone who wrote a change that is fixed or reverted by you now
      • who commented on related changes in the recent past
      • who otherwise has expertise and is interested in the topic
    • pull requests on github are only optional
  • post follow-up version(s) if feedback requires this

  • send reminder if nothing happened after about a week

Developer's Certificate of Origin 1.1

When signing-off a patch for this project like this

Signed-off-by: Random J Developer <>

using your real name (no pseudonyms or anonymous contributions), you declare the following:

By making a contribution to this project, I certify that:

    (a) The contribution was created in whole or in part by me and I
        have the right to submit it under the open source license
        indicated in the file; or

    (b) The contribution is based upon previous work that, to the best
        of my knowledge, is covered under an appropriate open source
        license and I have the right under that license to submit that
        work with modifications, whether created in whole or in part
        by me, under the same open source license (unless I am
        permitted to submit under a different license), as indicated
        in the file; or

    (c) The contribution was provided directly to me by some other
        person who certified (a), (b) or (c) and I have not modified

    (d) I understand and agree that this project and the contribution
        are public and that a record of the contribution (including all
        personal information I submit with it, including my sign-off) is
        maintained indefinitely and may be redistributed consistent with
        this project or the open source license(s) involved.

See also (Section 11, "Sign your work") for further background on this process which was adopted from the Linux kernel.

Contribution Integration Process

  1. patch reviews performed on mailing list

    • at least by maintainers, but everyone is invited
    • feedback has to consider design, functionality and style
    • simpler and clearer code preferred, even if original code works fine
  2. accepted patches merged into next branch

  3. further testing done by community, including CI build tests and code analyzer runs

  4. if no new problems or discussions showed up, acceptance into master

    • grace period for master: about 3 days
    • urgent fixes may be applied sooner

github facilities are not used for the review process so that people can follow all changes and related discussions at a single stop, the mailing list. This may change in the future if github should improve their email integration.

Areas of responsibility

Jailhouse is rather small. Nevertheless, there are different people involved in different areas of its code. The following list shall give an overview on who is working in which area and should be involved when discussing changes:

Jan Kiszka

  • overall Jailhouse maintenance
  • committer to official repository

Valentine Sinitsyn

  • AMD64 support

Henning Schild

  • inter-cell communication
  • configuration file generator

Ralf Ramsauer

  • uart infrastructure
  • inmate library