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 9C02EC7EE23 for ; Tue, 30 May 2023 07:57:05 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1q3uDK-0001Oe-UB; Tue, 30 May 2023 03:56:19 -0400 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 1q3uDH-0001OT-AZ for qemu-devel@nongnu.org; Tue, 30 May 2023 03:56:15 -0400 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 1q3uDE-00043U-0v for qemu-devel@nongnu.org; Tue, 30 May 2023 03:56:14 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685433370; 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: in-reply-to:in-reply-to:references:references; bh=eCzA3naR0xjphXPwyKjaBf7yrKHIVk3sTeexl0+087I=; b=e1tnfu3owFsIeWeu8qWkzUyindfZEim4NsEJ/T4THdsVM6xKcUtNPNUBLLLWREu4I4asA7 KkJnCludTpXP0Qo1pTsdHjUXQHAPutBOK7TCB5Aqml7Gq7nHSCIRxb/IZH91N5dx5O/lUf AEWuDxp6Crm0CCYDy3W5/YN7TgSFFaU= 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-650-b8NF-_sQP_qkIfJCuDIIZA-1; Tue, 30 May 2023 03:56:07 -0400 X-MC-Unique: b8NF-_sQP_qkIfJCuDIIZA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 18A9A101B047; Tue, 30 May 2023 07:56:07 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.91]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E96682166B25; Tue, 30 May 2023 07:56:06 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id D93CD21E692E; Tue, 30 May 2023 09:56:05 +0200 (CEST) From: Markus Armbruster To: Het Gala Cc: qemu-devel@nongnu.org, prerna.saxena@nutanix.com, quintela@redhat.com, dgilbert@redhat.com, pbonzini@redhat.com, berrange@redhat.com, eblake@redhat.com, manish.mishra@nutanix.com, aravind.retnakaran@nutanix.com Subject: Re: [PATCH v5 1/9] migration: introduced 'MigrateAddress' in QAPI for migration wire protocol. References: <20230519094617.7078-1-het.gala@nutanix.com> <20230519094617.7078-2-het.gala@nutanix.com> <87sfbkjow3.fsf@pond.sub.org> <87edmyuwzc.fsf@pond.sub.org> <99b3e516-2a4a-aa48-8bc2-7bb886b8db52@nutanix.com> Date: Tue, 30 May 2023 09:56:05 +0200 In-Reply-To: <99b3e516-2a4a-aa48-8bc2-7bb886b8db52@nutanix.com> (Het Gala's message of "Tue, 30 May 2023 13:02:27 +0530") Message-ID: <878rd6tfqi.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 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 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: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.16, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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 Het Gala writes: > On 30/05/23 12:28 pm, Markus Armbruster wrote: >> Het Gala writes: >> >>> On 25/05/23 11:04 pm, Markus Armbruster wrote: [...] >>>> Aside: a more powerful type system would let us extend SocketAddress >>>> with additional variants instead of wrapping it in a union. >>> >>> Markus, what do you mean by additional variants here in context of socket? Can you give a small example. >> >> As is, we have a nest of two unions: >> >> * The outer union has branches @socket, @exec, @rdma. >> >> * Branch @socket is the inner union, it has branches @inet, @unix, ... >> >> A more powerful type system would let us extend SocketAddress instead, >> so MigrateAddress has everything SocketAddress has, plus additional >> branches @exec, @rdma. Naturally, the type of the discriminator also >> needs to be extended, so that it has everything SocketAddress's >> discriminator type has, plus additional members @exec, @rdma. > > Okay, so you mean something like : > > +# Since 8.1 > +## > +{ 'union': 'MigrateAddress', > + 'base': { 'transport' : 'MigrateTransport'}, > + 'discriminator': 'transport', > + 'data': { > + 'inet': 'InetSocketAddress', > + 'unix': 'UnixSocketAddress', > + 'vsock': 'VsockSocketAddress', > + 'fd': 'str', > + 'exec': 'MigrateExecCommand', > + 'rdma': 'InetSocketAddress' } } > > Even I agree that directly leveraging this is the best option, but then wouldn't it introduce redundancy ? we would not be able to leverage socket union right in that case or am I missing something. Yes, there's redundancy, due to QAPI's insufficient expressive power. Is the cleaner external interface worth the (internal) redundancy, and possibly coding complications that go with it?