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 09868C05027 for ; Fri, 17 Feb 2023 15:56:40 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pT35i-0005zJ-Vo; Fri, 17 Feb 2023 10:56:07 -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 1pT35h-0005xc-D5 for qemu-devel@nongnu.org; Fri, 17 Feb 2023 10:56:05 -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 1pT35e-0007oj-B8 for qemu-devel@nongnu.org; Fri, 17 Feb 2023 10:56:04 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1676649361; h=from:from: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=eArkmVMdZXZHRRXJ5jzEQZYdROFfj80uUaI7uNepmiE=; b=NIOTA/3shC0Ucm1Z8E4SuGeLNz+54zfnuCI/H6Uymgpfud+TD4k9DfhVqU0VzBiOxElo/F Odf+LbHDgGosDrtY/IeN+/rMVHNyWrF7IMwawvs07Mk2QNiArVTClfvgD/Xv3UsK+XJwtj Zt9BBMiQKLRRpF2+EzxdZwi1bOqjrjE= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-630-b-MgQLS1NjeTeXiPfNX8fA-1; Fri, 17 Feb 2023 10:55:59 -0500 X-MC-Unique: b-MgQLS1NjeTeXiPfNX8fA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id C5748858F0E; Fri, 17 Feb 2023 15:55:58 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.25]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 85FF61121315; Fri, 17 Feb 2023 15:55:58 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 8114221E6A1F; Fri, 17 Feb 2023 16:55:57 +0100 (CET) From: Markus Armbruster To: Paolo Bonzini Cc: qemu-devel@nongnu.org, Daniel P . =?utf-8?Q?Berrang=C3=A9?= , Peter Maydell , John Snow , Kevin Wolf Subject: Re: [RFC PATCH] docs: build-platforms: refine requirements on Python build dependencies References: <20230217124150.205012-1-pbonzini@redhat.com> Date: Fri, 17 Feb 2023 16:55:57 +0100 In-Reply-To: <20230217124150.205012-1-pbonzini@redhat.com> (Paolo Bonzini's message of "Fri, 17 Feb 2023 13:41:50 +0100") Message-ID: <87pma870c2.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Paolo Bonzini writes: > 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). > > 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). > > Assuming QEMU would like to move forward with the deprecation of > Python 3.6 (for which there are some good reasons: completing the > configure->meson switch, which requires Meson 0.63, or making qapidoc I think you mean "the QAPI generator". > fully typed which requires newer versions of mypy and also Python due > to PEP563), 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 suppo= rt > 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 understa= nd > for developers, this is difficult to apply because qapidoc runs at Suggest "some QAPI generator code runs". > sphinx-build time, and it is 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 two 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 limits the support period for non-native dependencies to a fixed > amount of 4 years. This is intended to be close to the Python 5-year > lifecycle while accounting for the time between a distro's feature free= ze > and the day it's released. This limit applies to all distro versions, > not just the previous one, in order to cater for the delay of SLE 16. > > The 4 year cutoff in practice means that QEMU will be able to drop Python > 3.6 support for QEMU 7.1 (RHEL8 becomes 4 year old next May, while SLE We released 7.1 last August, do you mean 8.0 or 8.1? > is already over the threshold). > > Note that all "non-native" packages are currently build dependencies. > If in the future some non-native packages became runtime dependencies for > parts of QEMU, it would still be possible to choose any of the first > three possibilities for them. > > Another possible future change is to the way that these dependencies > have to be obtained by the person building QEMU. Right now they have to > run pip before the build; it may be desirable for configure to set up a > virtual environment and download them in the same way that it populates > git submodules. 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 with > pip would remain for people whose build machines lack network access. > The change to the support policy neither requires nor forbids this change. > > [Thanks to Daniel P. Berrang=C3=A9, Peter Maydell and others for discussi= ons > that were copied or summarized in the above commit message] > > Cc: Markus Armbruster > Cc: Daniel P. Berrang=C3=A9 > Cc: Peter Maydell > Cc: John Snow > Cc: Kevin Wolf > Signed-off-by: Paolo Bonzini > --- > docs/about/build-platforms.rst | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/docs/about/build-platforms.rst b/docs/about/build-platforms.= rst > index 1c1e7b9e11c3..e1ea09789107 100644 > --- a/docs/about/build-platforms.rst > +++ b/docs/about/build-platforms.rst > @@ -86,6 +86,25 @@ respective ports repository, while NetBSD will use the= pkgsrc repository. > For macOS, `Homebrew`_ will be used, although `MacPorts`_ is expected to= carry > similar versions. >=20=20 > +Python build dependencies > +~~~~~~~~~~~~~~~~~~~~~~~~~ > + > +The minimum supported version of Python is currently 3.6. > + > +Distributions with long-term support often provide multiple > +versions of the Python runtime. QEMU aims to support the default > +Python runtime for 4 years after the initial release of a new version. Just to be crystal clear: new version of what? > +Afterwards, you may have to point QEMU to a newer version of the Python > +runtime using the ``--python`` command line option of the ``configure`` > +script. > + > +Some of QEMU's build dependencies are written in Python and available > +through the Python Package Index (PyPI). QEMU aims to be compatible > +with the versions packaged by common Linux distributions for the first > +4 years after the major release of the distribution. After 4 years, > +you may have to use ``pip`` to install some of these build dependencies. > + > + > Windows > -------