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 A7DACCD1283 for ; Fri, 29 Mar 2024 19:45:38 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rqI9i-0006fq-Rn; Fri, 29 Mar 2024 15:44:51 -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 1rqI9f-0006fD-5b for qemu-devel@nongnu.org; Fri, 29 Mar 2024 15:44:47 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rqI9d-0004lL-9R for qemu-devel@nongnu.org; Fri, 29 Mar 2024 15:44:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1711741483; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=V11yvYk7eJymAL7pJOm/k1LWAhKluBtXgiPc5016mLE=; b=c++fu9KOipBvUEwuPGc/HdD/mEJlUT0wl3cp6z0+kh/kraWHVly6sRbb3wp3huoAMOXKyM rVQvJTWOTpkoFZRJTT1aocYfJE20kIHBm51yAuTQr7hdCnmciphAk2IeKGQXMiNQ2vcPbm CpcASU1MczSNvqvk1kIfhEWhnGF08tY= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-385-tiHPQzpEPlKYd6LUZG7gvg-1; Fri, 29 Mar 2024 15:44:39 -0400 X-MC-Unique: tiHPQzpEPlKYd6LUZG7gvg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (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 mimecast-mx02.redhat.com (Postfix) with ESMTPS id D2C041C07547; Fri, 29 Mar 2024 19:44:38 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.9]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8A4D4111E3F3; Fri, 29 Mar 2024 19:44:28 +0000 (UTC) Date: Fri, 29 Mar 2024 19:44:21 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Cc: "Zhijian Li (Fujitsu)" , Peter Xu , Fabiano Rosas , "qemu-devel@nongnu.org" , Yuval Shaia , Kevin Wolf , Prasanna Kumar Kalever , Cornelia Huck , Michael Roth , Prasanna Kumar Kalever , "integration@gluster.org" , Paolo Bonzini , "qemu-block@nongnu.org" , "devel@lists.libvirt.org" , Hanna Reitz , "Michael S. Tsirkin" , Thomas Huth , Eric Blake , Song Gao , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Markus Armbruster , Alex =?utf-8?Q?Benn=C3=A9e?= , Wainer dos Santos Moschetta , Beraldo Leal , Peter Maydell , Yu Zhang Subject: Re: [PATCH-for-9.1 v2 2/3] migration: Remove RDMA protocol handling Message-ID: References: <20240328130255.52257-1-philmd@linaro.org> <20240328130255.52257-3-philmd@linaro.org> <87frwatp7n.fsf@suse.de> <7a510fbe-1c27-4f67-93b8-0d9cf01c1c74@fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.3 Received-SPF: pass client-ip=170.10.129.124; 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=-0.099, 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 autolearn=unavailable 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, Mar 29, 2024 at 11:28:54AM +0100, Philippe Mathieu-Daudé wrote: > Hi Zhijian, > > On 29/3/24 02:53, Zhijian Li (Fujitsu) wrote: > > > > > > On 28/03/2024 23:01, Peter Xu wrote: > > > On Thu, Mar 28, 2024 at 11:18:04AM -0300, Fabiano Rosas wrote: > > > > Philippe Mathieu-Daudé writes: > > > > > > > > > The whole RDMA subsystem was deprecated in commit e9a54265f5 > > > > > ("hw/rdma: Deprecate the pvrdma device and the rdma subsystem") > > > > > released in v8.2. > > > > > > > > > > Remove: > > > > > - RDMA handling from migration > > > > > - dependencies on libibumad, libibverbs and librdmacm > > > > > > > > > > Keep the RAM_SAVE_FLAG_HOOK definition since it might appears > > > > > in old migration streams. > > > > > > > > > > Cc: Peter Xu > > > > > Cc: Li Zhijian > > > > > Acked-by: Fabiano Rosas > > > > > Signed-off-by: Philippe Mathieu-Daudé > > > > > > > > Just to be clear, because people raised the point in the last version, > > > > the first link in the deprecation commit links to a thread comprising > > > > entirely of rdma migration patches. I don't see any ambiguity on whether > > > > the deprecation was intended to include migration. There's even an ack > > > > from Juan. > > > > > > Yes I remember that's the plan. > > > > > > > > > > > So on the basis of not reverting the previous maintainer's decision, my > > > > Ack stands here. > > > > > > > > We also had pretty obvious bugs ([1], [2]) in the past that would have > > > > been caught if we had any kind of testing for the feature, so I can't > > > > even say this thing works currently. > > > > > > > > @Peter Xu, @Li Zhijian, what are your thoughts on this? > > > > > > Generally I definitely agree with such a removal sooner or later, as that's > > > how deprecation works, and even after Juan's left I'm not aware of any > > > other new RDMA users. Personally, I'd slightly prefer postponing it one > > > more release which might help a bit of our downstream maintenance, however > > > I assume that's not a blocker either, as I think we can also manage it. > > > > > > IMHO it's more important to know whether there are still users and whether > > > they would still like to see it around. That's also one thing I notice that > > > e9a54265f533f didn't yet get acks from RDMA users that we are aware, even > > > if they're rare. According to [2] it could be that such user may only rely > > > on the release versions of QEMU when it broke things. > > > > > > So I'm copying Yu too (while Zhijian is already in the loop), just in case > > > someone would like to stand up and speak. > > > > > > I admit RDMA migration was lack of testing(unit/CI test), which led to the a few > > obvious bugs being noticed too late. > > However I was a bit surprised when I saw the removal of the RDMA migration. I wasn't > > aware that this feature has not been marked as deprecated(at least there is no > > prompt to end-user). > > > > > > > IMHO it's more important to know whether there are still users and whether > > > they would still like to see it around. > > > > Agree. > > I didn't immediately express my opinion in V1 because I'm also consulting our > > customers for this feature in the future. > > > > Personally, I agree with Perter's idea that "I'd slightly prefer postponing it one > > more release which might help a bit of our downstream maintenance" > > Do you mind posting a deprecation patch to clarify the situation? The key thing the first deprecation patch missed was that it failed to issue a warning message when RDMA migration was actually used. 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 :|