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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7053FC47404 for ; Mon, 7 Oct 2019 12:40:31 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 44C20205F4 for ; Mon, 7 Oct 2019 12:40:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 44C20205F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:44196 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iHSJS-0003G2-DM for qemu-devel@archiver.kernel.org; Mon, 07 Oct 2019 08:40:30 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:51206) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iHSFD-0007KY-CZ for qemu-devel@nongnu.org; Mon, 07 Oct 2019 08:36:09 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iHSFA-00077F-Nj for qemu-devel@nongnu.org; Mon, 07 Oct 2019 08:36:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35782) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iHSFA-00076r-Ff for qemu-devel@nongnu.org; Mon, 07 Oct 2019 08:36:04 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9BF56757C0; Mon, 7 Oct 2019 12:36:02 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.36.118.123]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CDB0E5C223; Mon, 7 Oct 2019 12:35:50 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 4EBFC1138648; Mon, 7 Oct 2019 14:35:45 +0200 (CEST) From: Markus Armbruster To: Peter Maydell Subject: Re: [PATCH] netmap: support git-submodule build otption References: <874l13qmvb.fsf@dusky.pond.sub.org> <20191004130242.27267-1-g.lettieri@iet.unipi.it> <87pnj8ltih.fsf@dusky.pond.sub.org> Date: Mon, 07 Oct 2019 14:35:45 +0200 In-Reply-To: (Peter Maydell's message of "Mon, 7 Oct 2019 12:58:38 +0100") Message-ID: <87zhicg2ce.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Mon, 07 Oct 2019 12:36:03 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Daniel P . Berrange" , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Jason Wang , QEMU Developers , Vincenzo Maffione , Giuseppe Lettieri , Stefan Hajnoczi , Giuseppe Lettieri , Luigi Rizzo Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Peter Maydell writes: > On Mon, 7 Oct 2019 at 11:50, Markus Armbruster wrote: >> Peter Maydell writes: >> > Basically new submodules are a pain so we seek to minimize >> > the use of them. >> >> I suggested making it a submodule upthread[*]. Let me try to distill >> the conversation into a rationale. Giuseppe, please correct mistakes. >> >> To make use of QEMU's netmap backend (CONFIG_NETMAP), you have to build >> and install netmap software from sources[**]. Which pretty much ensures >> developers compile with CONFIG_NETMAP off, and the code rots. >> >> For other dependencies that aren't readily available on common >> development hosts (slirp, capstone), we use submodules to avoid such >> rot. If the system provides, we use that, and if it doesn't, we fall >> back to the submodule. This has served us well. > > I would put this differently. We don't use submodules to avoid > code-rot. We use submodules where a dependency is needed for us > to provide QEMU features that are sufficiently important that we > want to provide them to users even if those users don't have the > dependency available to them as a system library. > > There are lots of features of QEMU that only compile with sufficiently > recent versions of dependencies, and we don't try to submodule-ize > them because the features aren't really that important for the bulk > of our users. For instance, we provided pixman as a submodule for > a while because the features that require it (our graphics layer > code) are important to almost all users. But we didn't provide > spice as a module even when you pretty much needed to be > running bleeding-edge redhat to satisfy the version dependency > we had, because most users don't care about spice support. > Shipping our dependencies as submodules imposes real costs > on the project (for instance we then need to track the upstream > to see when we should be updating, including checking whether > we need to update to fix security issues). Submodules should be > the exception, not the rule. > >> For netmap, falling back to the submodule when the host doesn't provide >> tends not to be useful beyond compile-testing. Because of that, we fall >> back only when the user explicitly asks for it by passing >> --enable-netmap=git to configure. CI should do that. > > This sounds like netmap is in the same position as most of our > dependencies: OK to compile if the system provides the library, > but if the system doesn't then almost all users won't care > that the feature isn't present. If CI of the QEMU code is useful, If CI of QEMU code isn't useful, then I suspect the QEMU code isn't useful, period. Giuseppe assures us the netmap QEMU code *is* useful. It followe we better make sure our CI covers it. A submodule would make sure, but it looks like it won't fly. So let's try another tack: > get the library supported by and shipped in distros. If you can't > get anybody in a distro (Linux or BSD) to care enough to ship the > library, this is a really niche feature, and up for consideration > for deprecate-and-drop from QEMU, I think. Giuseppe, you mentioned netmap is in FreeBSD, and getting it into Linux is unlikely, so let's focus on FreeBSD. We have a FreeBSD section in .patchew.yml, which makes me guess Patchew CI tests FreeBSD. Does it test with CONFIG_NETMAP out of the box? If not, how do we have to tweak its configuration to get CONFIG_NETMAP enabled? Who could help with this?