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 C9FB7C531DC for ; Fri, 16 Aug 2024 15:38:11 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sez0s-0007O9-FM; Fri, 16 Aug 2024 11:37:14 -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 1sez0r-0007N3-80 for qemu-devel@nongnu.org; Fri, 16 Aug 2024 11:37:13 -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 1sez0p-00023q-CG for qemu-devel@nongnu.org; Fri, 16 Aug 2024 11:37:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1723822628; 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:in-reply-to:in-reply-to: references:references; bh=AvvrFVsdOg9uRM0iTO/AB1LG3//W4g3kxWvbRksjHXY=; b=AT7enmihCRWwDVVA79UdPUgjJCnFSyYFhyoZRnfBhs8DIFLHwqd3r/ngyhLvR2QgIl3u6w FD3hBpBKYkPls00x6QVLN1GQ+a3f3trHzra0QdlgeWsAJ5M7ZByzWV5J31CI+iN2Z66tTP NUBAFJuE5pO9UwpTcZD2+Wy3/SObjUw= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-304-XQvVMK0LM3Kyys3h8muuIA-1; Fri, 16 Aug 2024 11:37:05 -0400 X-MC-Unique: XQvVMK0LM3Kyys3h8muuIA-1 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id EE40B195422E; Fri, 16 Aug 2024 15:37:03 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.143]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id ACF0B1956052; Fri, 16 Aug 2024 15:37:01 +0000 (UTC) Date: Fri, 16 Aug 2024 16:36:58 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Xu Cc: Steven Sistare , qemu-devel@nongnu.org, Fabiano Rosas , Markus Armbruster Subject: Re: [RFC V1 0/6] Live update: cpr-transfer Message-ID: References: <1719776648-435073-1-git-send-email-steven.sistare@oracle.com> <90a01b2b-6a72-475f-9232-3af73d1618cf@oracle.com> <94478262-034d-48db-bd4d-c74ca3c315a6@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 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: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.131, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: , 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 Fri, Aug 16, 2024 at 11:23:01AM -0400, Peter Xu wrote: > On Fri, Aug 16, 2024 at 11:13:36AM -0400, Steven Sistare wrote: > > On 8/15/2024 4:28 PM, Peter Xu wrote: > > > On Sat, Jul 20, 2024 at 04:07:50PM -0400, Steven Sistare wrote: > > > > > > The new user-visible interfaces are: > > > > > > * cpr-transfer (MigMode migration parameter) > > > > > > * cpr-uri (migration parameter) > > > > > > > > > > I wonder whether this parameter can be avoided already, maybe we can let > > > > > cpr-transfer depend on unix socket in -incoming, then integrate fd sharing > > > > > in the same channel? > > > > > > > > You saw the answer in another thread, but I repeat it here for others benefit: > > > > > > > > "CPR state cannot be sent over the normal migration channel, because devices > > > > and backends are created prior to reading the channel, so this mode sends > > > > CPR state over a second migration channel that is not visible to the user. > > > > New QEMU reads the second channel prior to creating devices or backends." > > > > > > Today when looking again, I wonder about the other way round: can we make > > > the new parameter called "-incoming-cpr", working exactly the same as > > > "cpr-uri" qemu cmdline, but then after cpr is loaded it'll be automatically > > > be reused for migration incoming ports? > > > > > > After all, cpr needs to happen already with unix sockets. Having separate > > > cmdline options grants user to make the other one to be non-unix, but that > > > doesn't seem to buy us anything.. then it seems easier to always reuse it, > > > and restrict cpr-transfer to only work with unix sockets for incoming too? > > > > This idea also occurred to me, but I dislike the loss of flexibility for > > the incoming socket type. The exec URI in particular can do anything, and > > we would be eliminating it. > > Ah, I would be guessing that if Juan is still around then exec URI should > already been marked deprecated and prone to removal soon.. while I tend to > agree that exec does introduce some complexity meanwhile iiuc nobody uses > that in production systems. > > What's the exec use case you're picturing? Would that mostly for debugging > purpose, and would that be easily replaceable with another tunnelling like > "ncat" or so? Conceptually "exec:" is a nice thing, but from a practical POV it introduces difficulties for QEMU. QEMU doesn't know if the exec'd command will provide a unidirectional channel or bidirectional channel, so has to assume the worst - unidirectional. It also can't know if it is safe to run the exec multiple times, or is only valid to run it once - so afgai nhas to assume once only. We could fix those by adding further flags in the migration address to indicate if its bi-directional & multi-channel safe. Technically "exec" is obsolete given "fd", but then that applies to literally all protocols. Implementing them in QEMU is a more user friendly thing. Exec was more compelling when QEMU's other protocols were less mature, lacking TLS for example, but I still find it interesting as a facility. 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 :|