Re: [PATCH v1 0/4] Stabilize Oxenstored's interface with

[Christian Lindig <christian.lindig@xxxxxxxxx>]

> On 22 Aug 2024, at 10:06, Andrii Sultanov <andrii.sultanov@xxxxxxxxx> wrote:
> 
> Oxenstored depends on unstable Xenctrl, utilizing only a few of its
> functions. This patch series introduces a dynamically-loaded OCaml
> plugin that aims to stabilize 'Xenctrl.domain_getinfo' and
> 'Xenctrl.domain_getinfolist' by hiding the instability behind a versioned
> interface.
> 
> This, in turn, would allow to fork Oxenstored out of the xen tree,
> speeding up its development and allowing it to transition to an
> OCaml-standard build system.
> 
> This is only one step towards the long-term goal of being able to drop
> libxenctrl: https://gitlab.com/xen-project/xen/-/issues/190
> 
> Commits and notes further in the patches explain the exact mechanism behind
> this. I've tested this oxenstored with a V2 interface and plugin, with V1
> plugin continuing to be compiled, loaded, and working correctly.
> 
> A dynamic-loading approach was chosen because it allows one to easily review
> the remaining usages of Xenctrl and does not force oxenstored to be recompiled
> every time xen changes.
> 
> This patch series passed the Gitlab CI
> (https://gitlab.com/xen-project/people/asultanov/xen/-/pipelines/1421643375),
> and was further tested on some hosts.
> 
> Oxenstored currently uses the single-domain 'domain_getinfo' function,
> whereas Cxenstored uses the more-efficient 'domain_getinfolist'. Both of
> these are provided in the plugin to allow a transition from one to the
> other without modifying the interface in the future.
> 
> A prototype of oxenstored using domain_getinfolist was also developed,
> though it is not a part of the current patch series. It also passed the
> Gitlab CI and was tested on hosts.
> (https://gitlab.com/xen-project/people/asultanov/xen/-/pipelines/1421686622)
> 
> A Gitlab repository with these patches applied, if it's easier for
> anyone to review it on there:
> https://gitlab.com/xen-project/people/asultanov/xen/-/compare/staging...staging?from_project_id=2336572
> 
> Andrii Sultanov (4):
>  tools/ocaml/common.make: Remove '-cc $(CC)' flag from OCAMLOPTFLAGS
>  ocaml/libs: Implement a dynamically-loaded plugin for
>    Xenctrl.domain_getinfo
>  tools/oxenstored: Use the plugin for Xenctrl.domain_getinfo
>  Makefile.rules: Fix OCaml libs
> 
> Config.mk                                     |   2 +-
> configure                                     |   7 +
> m4/paths.m4                                   |   4 +
> tools/configure                               |   7 +
> tools/ocaml/Makefile                          |   1 +
> tools/ocaml/Makefile.rules                    |  21 ++-
> tools/ocaml/common.make                       |   2 +-
> tools/ocaml/libs/Makefile                     |   2 +-
> tools/ocaml/libs/xenstoredglue/META.in        |   4 +
> tools/ocaml/libs/xenstoredglue/Makefile       |  39 ++++
> .../domain_getinfo_plugin_v1/META.in          |   5 +
> .../domain_getinfo_plugin_v1/Makefile         |  38 ++++
> .../domain_getinfo_stubs_v1.c                 | 169 ++++++++++++++++++
> .../domain_getinfo_v1.ml                      |  51 ++++++
> .../domain_getinfo_v1.mli                     |   0
> .../libs/xenstoredglue/plugin_interface_v1.ml |  25 +++
> .../xenstoredglue/plugin_interface_v1.mli     |  34 ++++
> tools/ocaml/xenstored/Makefile                |   5 +-
> tools/ocaml/xenstored/domains.ml              |  63 +++++--
> tools/ocaml/xenstored/paths.ml.in             |   1 +
> 20 files changed, 454 insertions(+), 26 deletions(-)
> create mode 100644 tools/ocaml/libs/xenstoredglue/META.in
> create mode 100644 tools/ocaml/libs/xenstoredglue/Makefile
> create mode 100644 
> tools/ocaml/libs/xenstoredglue/domain_getinfo_plugin_v1/META.in
> create mode 100644 
> tools/ocaml/libs/xenstoredglue/domain_getinfo_plugin_v1/Makefile
> create mode 100644 
> tools/ocaml/libs/xenstoredglue/domain_getinfo_plugin_v1/domain_getinfo_stubs_v1.c
> create mode 100644 
> tools/ocaml/libs/xenstoredglue/domain_getinfo_plugin_v1/domain_getinfo_v1.ml
> create mode 100644 
> tools/ocaml/libs/xenstoredglue/domain_getinfo_plugin_v1/domain_getinfo_v1.mli
> create mode 100644 tools/ocaml/libs/xenstoredglue/plugin_interface_v1.ml
> create mode 100644 tools/ocaml/libs/xenstoredglue/plugin_interface_v1.mli
> 
> -- 
> 2.39.2
> 

Acked-by: Christian Lindig <christian.lindig@xxxxxxxxx>

I fully support the direction this is taking: decoupling Oxenstore from the Xen 
tree to hopefully speed up the development cycle and to attract OCaml 
developers by moving to a more OCaml-idiomatic build system. The code was 
previously shared with me.

— C