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 99C62C38142 for ; Fri, 27 Jan 2023 21:27:19 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pLWEq-00075W-GC; Fri, 27 Jan 2023 16:26:24 -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 1pLWEo-00074o-Pg for qemu-devel@nongnu.org; Fri, 27 Jan 2023 16:26:22 -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 1pLWEm-0000Ap-Vj for qemu-devel@nongnu.org; Fri, 27 Jan 2023 16:26:22 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674854779; 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; bh=5joQAFDvnzFVS4QE265Iy6mQ5n6ABt7DgSb2bnviCF8=; b=KxqYvwm6nTKFMzg9pLp3s6LqhzoyPMnhgdhyWgZDKIS6vNX1j3YZGKEE2MuDc5x3ApiApw /uBhyaL8qfmM48y84Oc+fE/mtTnz4cieMtlJTpHhAUVzk6KWOOIRFhY7I2wk45J1Wv1/mg qON7WdoSZCIqggQWYHvyWXQtNDUnHpo= 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-352-ucvhHb5LMcS19ARI87Vndw-1; Fri, 27 Jan 2023 16:26:18 -0500 X-MC-Unique: ucvhHb5LMcS19ARI87Vndw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D0D5E29AA3B3; Fri, 27 Jan 2023 21:26:17 +0000 (UTC) Received: from redhat.com (unknown [10.2.17.173]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 58ECA492C14; Fri, 27 Jan 2023 21:26:17 +0000 (UTC) Date: Fri, 27 Jan 2023 15:26:15 -0600 From: Eric Blake To: qemu-devel@nongnu.org, qemu-block@nongnu.org Cc: berrange@redhat.com, rjones@redhat.com, kwolf@redhat.com Subject: RFC: towards systemd socket activation in q-s-d Message-ID: <20230127212233.k6rlqkmubhovjxs4@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: NeoMutt/20220429 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Received-SPF: pass client-ip=170.10.133.124; envelope-from=eblake@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 In https://bugzilla.redhat.com/show_bug.cgi?id=2055229, the question was raised on how to make qemu-storage-daemon sufficiently powerful to be a full-blown replacement to qemu-nbd. One of the features still lacking is the ability to do systemd socket activation (qemu-nbd does this, qemu-storage-daemon needs a way to do it). But that bug further noted that systemd supports LISTEN_FDNAMES to supply names to a passed-in fd (right now, qemu-nbd does not use names, but merely expects one fd in LISTEN_FDS). Dan had the idea that it would be nice to write a systemd file that passes in a socket name for a QMP socket, as in: [Socket] ListenStream=/var/run/myapp/qsd.qmp FileDescriptorName=qmp Service=myapp-qsd.service and further notes that QAPI SocketAddressType supports @fd which is a name in QMP (a previously-added fd passed through the older 'getfd' command, rather than the newer 'add-fd' command), but an integer on the command line. With LISTEN_FDNAMES, we could mix systemd socket activation with named fds for any command line usage that already supports SocketAddressType (not limited to just q-s-d usage). I'm at a point where I can take a shot at implementing this, but want some feedback on whether it is better to try to shoehorn a generic solution into the existing @fd member of the SocketAddressType union, or whether it would be better to add yet another union member @systemd-fd or some similar name to make it explicit when a command line parameter wants to refer to an fd being passed through systemd socket activation LISTEN_FDS and friends. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org