From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 78AAAC636CC for ; Mon, 20 Feb 2023 15:03:37 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pU7h7-0000G2-TP; Mon, 20 Feb 2023 10:03:09 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pU7h4-0000DW-Gg for qemu-devel@nongnu.org; Mon, 20 Feb 2023 10:03:06 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pU7h1-0007li-L0 for qemu-devel@nongnu.org; Mon, 20 Feb 2023 10:03:06 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1676905382; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3teBsSQKa+u+kiDvtGs+8fMnMeVgHDV1QY5teQmeC+M=; b=XGMvzt0Cz7UcFBErcaC7kgqrcMLD7FIfRfzia/AYwLrbvGZ3WUtycB7Dvk5RQMKZzNsXDu Nmp6axsKsccCU0kn/TPjbrBMRsmv9tRL9vULwLBrgJEYw1RAV6PhT9nYBvt4pfPUOmxxoS kLM2o4jWri08+W9f6T0t+J0968XElE4= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-602-hwIsj22YPVytlyvIxMLW9A-1; Mon, 20 Feb 2023 10:02:58 -0500 X-MC-Unique: hwIsj22YPVytlyvIxMLW9A-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 334CC299E741; Mon, 20 Feb 2023 15:02:58 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.52]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BB5874015319; Mon, 20 Feb 2023 15:02:56 +0000 (UTC) Date: Mon, 20 Feb 2023 15:02:50 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Paolo Bonzini Cc: qemu-devel@nongnu.org, thuth@redhat.com, Markus Armbruster , Peter Maydell , John Snow , Kevin Wolf Subject: Re: [RFC PATCH v2] docs: build-platforms: refine requirements on Python build dependencies Message-ID: References: <20230220142942.287392-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230220142942.287392-1-pbonzini@redhat.com> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Feb 20, 2023 at 03:29:42PM +0100, Paolo Bonzini wrote: > Historically, the critical dependency for both building and running > QEMU has been the distro packages. Because QEMU is written in C and C's > package management has been tied to distros (at least if you do not want > to bundle libraries with the binary, otherwise I suppose you could use > something like conda or wrapdb), C dependencies of QEMU would target the > version that is shipped in relatively old but still commonly used distros. > > For non-C libraries, however, the situation is different, as these > languages have their own package management tool (cpan, pip, gem, npm, > and so on). For some of these languages, the amount of dependencies > for even a simple program can easily balloon to the point that many > distros have given up on packaging non-C code. For this reason, it has > become increasingly normal for developers to download dependencies into > a self-contained local environment, instead of relying on distro packages. > > Fortunately, this affects QEMU only at build time, as qemu.git does > not package non-C artifacts such as the qemu.qmp package; but still, > as we make more use of Python, we experience a clash between a support > policy that is written for the C world, and dependencies (both direct > and indirect) that increasingly do not care for the distro versions > and are quick at moving past Python runtime versions that are declared > end-of-life. > > For example, Python 3.6 has been EOL'd since December 2021 and Meson 0.62 > (released the following March) already dropped support for it. Yet, > Python 3.6 is the default version of the Python runtime for RHEL/CentOS > 8 and SLE 15, respectively the penultimate and the most recent version > of two distros that QEMU would like to support. (It is also the version > used by Ubuntu 18.04, but QEMU stopped supporting it in April 2022). > > There are good reasons to move forward with the deprecation of Python > 3.6 in QEMU as well: completing the configure->meson switch (which > requires Meson 0.63), and making the QAPI generator fully typed (which > requires newer versions of not just mypy but also Python, due to PEP563). > > Fortunately, these long-term support distros do include newer versions of > the Python runtime. However, these more recent runtimes only come with > a very small subset of the Python packages that the distro includes. > Because most dependencies are optional tests (avocado, mypy, flake8) > and Meson is bundled with QEMU, the most noticeably missing package is > Sphinx (and the readthedocs theme). There are four possibilities: > > * we change the support policy and stop supporting CentOS 8 and SLE 15; > not a good idea since CentOS 8 is not an unreasonable distro for us to > want to continue to support > > * we keep supporting Python 3.6 until CentOS 8 and SLE 15 stop being > supported. This is a possibility---but we may want to revise the support > policy anyway because SLE 16 has not even been released, so this would > mean delaying those desirable reasons for perhaps three years; > > * we support Python 3.6 just for building documentation, i.e. we are > careful not to use Python 3.7+ features in our Sphinx extensions but are > free to use them elsewhere. Besides being more complicated to understand > for developers, this can be quite limiting; parts of the QAPI generator > run at sphinx-build time, which would exclude one of the areas which > would benefit from a newer version of the runtime; > > * we only support Python 3.7+, which means CentOS 8 CI and users > have to either install Sphinx from pip or disable documentation. > > This proposed update to the support policy chooses the last of these > possibilities. It does by modifying three aspects of the support > policy: > > * it introduces different support periods for *native* vs. *non-native* > dependencies. Non-native dependencies are currently Python ones only, > and for simplicity the policy only mentions Python; however, the concept > generalizes to other languages with a well-known upstream package > manager, that users of older distributions can fetch dependencies from; > > * it opens up the possibility of taking non-native dependencies from their > own package index instead of using the version in the distribution. The > wording right now is specific to dependencies that are only required at > build time. In the future we may have to refine it if, for example, parts > of QEMU will be written in Rust; in that case, crates would be handled > in a similar way to submodules and vendored in the release tarballs. > > * it mentions specifically that optional build dependencies are excluded > from the platform policy. Tools such as mypy don't affect the ability > to build QEMU and move fast enough that distros cannot standardize on > a single version of them (for example RHEL9 does not package them at > all, nor does it run them at rpmbuild time). In other cases, such as > cross compilers, we have alternatives. > > Right now, non-native dependencies have to be download manually by > running "pip" before "configure". In the future, it may be desirable Personally I'd write a stronger s/may/will/ given the feedback people have written on the problems they've hit with usage of pip in the global namespace. > for configure to set up a virtual environment and download them in the > same way that it populates git submodules (but, in this case, without > vendoring them in the release tarballs). > > Just like with submodules, this would make things easier for people > that can afford accessing the network in their build environment; the > option to populate the build environment manually would remain for > people whose build machines lack network access. The change to the > support policy neither requires nor forbids this future change. > > [Thanks to Daniel P. Berrangé, Peter Maydell and others for discussions > that were copied or summarized in the above commit message] > > Cc: Markus Armbruster > Cc: Daniel P. Berrangé > Cc: Peter Maydell > Cc: John Snow > Cc: Kevin Wolf > Signed-off-by: Paolo Bonzini > --- > docs/about/build-platforms.rst | 32 ++++++++++++++++++++++++++++++++ > 1 file changed, 32 insertions(+) Reviewed-by: Daniel P. Berrangé > > diff --git a/docs/about/build-platforms.rst b/docs/about/build-platforms.rst > index 1c1e7b9e11c3..5cc4e365344b 100644 > --- a/docs/about/build-platforms.rst > +++ b/docs/about/build-platforms.rst > @@ -86,6 +86,38 @@ respective ports repository, while NetBSD will use the pkgsrc repository. > For macOS, `Homebrew`_ will be used, although `MacPorts`_ is expected to carry > similar versions. > > +Some build dependencies may follow less conservative rules: > + > +Python runtime > + Distributions with long-term support often provide multiple versions > + of the Python runtime. While QEMU will initially aim to support the > + distribution's default runtime, it may later increase its minimum version > + to any newer python that is available as an option from the vendor. > + In this case, it will be necessary to use the ``--python`` command line > + option of the ``configure`` script to point QEMU to a supported > + version of the Python runtime. > + > + As of QEMU |version|, the minimum supported version of Python is 3.6. > + > +Python build dependencies > + Some of QEMU's build dependencies are written in Python. Usually these > + are only packages by distributions for the default Python runtime. s/packages/packaged/ > + If QEMU bumps its minimum Python version and a non-default runtime is > + required, it may be neccessary to fetch python modules from the Python > + Package Index (PyPI) via ``pip``, in order to build QEMU. > + > +Optional build dependencies > + Build components whose absence does not affect the ability to build > + QEMU may not be available in distros, or may be too old for QEMU's > + requirements. Many of these, such as the Avocado testing framework > + or various linters, are written in Python and therefore can also > + be installed using ``pip``. Cross compilers are another example > + of optional build-time dependency; in this case it is possible to > + download them from repositories such as EPEL, to use container-based > + cross compilation using ``docker`` or ``podman``, or to use pre-built > + binaries distributed with QEMU. > + > + > Windows > ------- > > -- > 2.39.1 > With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|