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=-8.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 D1798C64E7C for ; Wed, 2 Dec 2020 11:20:49 +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 2C28E22203 for ; Wed, 2 Dec 2020 11:20:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2C28E22203 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]:33642 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kkQBj-0003kk-Ur for qemu-devel@archiver.kernel.org; Wed, 02 Dec 2020 06:20:47 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:42790) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kkQAf-0002PW-P6 for qemu-devel@nongnu.org; Wed, 02 Dec 2020 06:19:41 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:42768) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kkQAc-0000Ka-K0 for qemu-devel@nongnu.org; Wed, 02 Dec 2020 06:19:41 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606907976; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6CoXM2pakNYyeJ42p0zgsVuRPL3cNcew9e+cosZFFks=; b=QgvsO5GkiYFyFx1P1qrgAPDrSOE2Z+VpkmdDNRu4nBmlwSJTQZVDCzkSCLgFnYJx0c0hrx vptWnG9OvovyPBJtf6zLR2gaFE/vbjLwZV4EqaJnV0lGLAvQ+Ougn0nu+UkDaYLnCT2gEI dpZ4FhdweGdGQ3G8wVowUQ155OFsE3g= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-290-feOSSCGYPX2G0CrA3i1N2g-1; Wed, 02 Dec 2020 06:19:34 -0500 X-MC-Unique: feOSSCGYPX2G0CrA3i1N2g-1 Received: by mail-wr1-f72.google.com with SMTP id b12so3400365wru.15 for ; Wed, 02 Dec 2020 03:19:34 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=6CoXM2pakNYyeJ42p0zgsVuRPL3cNcew9e+cosZFFks=; b=QBYRbeXKw+xX8rrsQ0rVoEdbWBR6UPFbNTI4GuZa1yzi6uYYCxAIcYXrGL0mJsgqgq e5diUb9Nq88bTEkte9FqH/K3UmHpqyI9VmUAXcrJ69Op6pq5bM2Aop4/+H+j0moyp7Ca sYeWN9veBBDzxJSkIBodAam6+Vv3WJ4oZlbKCKt/N63r1dW3XeZfEEdogd6DcBRT7oWD hrlsNITxdKiGKXohs/0ODgk2IwjJ1CBCVC9HggURUj+v2b52FfktzVsZF9skc/dXGvTY 6CDl7rFq2vD5nwd18zl0KRg1qMlE+bK/+ywjeJGEZAZN3w1St5Cryp3q+BmVCocgczvE jviw== X-Gm-Message-State: AOAM532XiKrEBJdzD2I8DM25YhAUT9LzoGwFtcxOS/1vwSs3cxUARgDv DhKwpn/SEM0yN6Zcjis3PIS2r0C3MC1W6vcW2JrgVBaoIA1Mswrr2ddf5CAgMsAzIQRVS0220qY /HtxLdllZLhN+Bk4= X-Received: by 2002:a1c:f311:: with SMTP id q17mr2591310wmq.28.1606907973208; Wed, 02 Dec 2020 03:19:33 -0800 (PST) X-Google-Smtp-Source: ABdhPJyu8Dfe00d0U76l17niHZay0khb3IRNHj5ND9t6EvievPSZZku5L/2h4oriOry6HE3CVwHY+A== X-Received: by 2002:a1c:f311:: with SMTP id q17mr2591285wmq.28.1606907972993; Wed, 02 Dec 2020 03:19:32 -0800 (PST) Received: from redhat.com (bzq-79-176-44-197.red.bezeqint.net. [79.176.44.197]) by smtp.gmail.com with ESMTPSA id y20sm1700261wma.15.2020.12.02.03.19.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Dec 2020 03:19:32 -0800 (PST) Date: Wed, 2 Dec 2020 06:19:29 -0500 From: "Michael S. Tsirkin" To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Subject: Re: [PATCH v2 01/27] migration: Network Failover can't work with a paused guest Message-ID: <20201202061641-mutt-send-email-mst@kernel.org> References: <20201118083748.1328-1-quintela@redhat.com> <20201118083748.1328-2-quintela@redhat.com> <20201202050918-mutt-send-email-mst@kernel.org> <20201202102718.GA2360260@redhat.com> <20201202053111-mutt-send-email-mst@kernel.org> <20201202053219-mutt-send-email-mst@kernel.org> <87mtywlbvq.fsf@secure.mitica> <20201202105515.GD2360260@redhat.com> MIME-Version: 1.0 In-Reply-To: <20201202105515.GD2360260@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.497, 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=ham autolearn_force=no X-Spam_action: no action 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: Eduardo Habkost , Juan Quintela , Jason Wang , "Dr. David Alan Gilbert" , qemu-devel@nongnu.org, Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Dec 02, 2020 at 10:55:15AM +0000, Daniel P. Berrangé wrote: > On Wed, Dec 02, 2020 at 11:51:05AM +0100, Juan Quintela wrote: > > "Michael S. Tsirkin" wrote: > > > On Wed, Dec 02, 2020 at 05:31:53AM -0500, Michael S. Tsirkin wrote: > > >> On Wed, Dec 02, 2020 at 10:27:18AM +0000, Daniel P. Berrangé wrote: > > >> > On Wed, Dec 02, 2020 at 05:13:18AM -0500, Michael S. Tsirkin wrote: > > >> > > On Wed, Nov 18, 2020 at 09:37:22AM +0100, Juan Quintela wrote: > > >> > > > If we have a paused guest, it can't unplug the network VF device, so > > >> > > > we wait there forever. Just change the code to give one error on that > > >> > > > case. > > >> > > > > > >> > > > Signed-off-by: Juan Quintela > > >> > > > > >> > > It's certainly possible but it's management that created > > >> > > this situation after all - why do we bother to enforce > > >> > > a policy? It is possible that management will unpause immediately > > >> > > afterwards and everything will proceed smoothly. > > >> > > > > >> > > Yes migration will not happen until guest is > > >> > > unpaused but the same it true of e.g. a guest that is stuck > > >> > > because of a bug. > > >> > > > >> > That's pretty different behaviour from how migration normally handles > > >> > a paused guest, which is that it is guaranteed to complete the migration > > >> > in as short a time as network bandwidth allows. > > >> > > > >> > Just ignoring the situation I think will lead to surprise apps / admins, > > >> > because the person/entity invoking the migration is not likely to have > > >> > checked wether this particular guest uses net failover or not before > > >> > invoking - they'll just be expecting a paused migration to run fast and > > >> > be guaranteed to complete. > > >> > > > >> > Regards, > > >> > Daniel > > >> > > >> Okay I guess. But then shouldn't we handle the reverse situation too: > > >> pausing guest after migration started but before device was > > >> unplugged? > > >> > > > > > > Thinking of which, I have no idea how we'd handle it - fail > > > pausing guest until migration is cancelled? > > > > > > All this seems heavy handed to me ... > > > > This is the minimal fix that I can think of. > > > > Further solution would be: > > - Add a new migration parameter: migrate-paused > > - change libvirt to use the new parameter if it exist > > - in qemu, when we do start migration (but after we wait for the unplug > > device) paused the guest before starting migration and resume it after > > migration finish. > > It would also have to handle issuing of paused after migration has > been started - delay the pause request until the nuplug is complete > is one answer. Hmm my worry would be that pausing is one way to give cpu resources back to host. It's problematic if guest can delay that indefinitely. > > My understanding talking with Laine is that they use this functionality > > by default for migration, saving, etc, i.e. it is not an isolated case. > > Yep, save-to-disk always runs in the paused state, and migration is > also paused by default unless the mgmt app explicitl asks for live > migration. > > 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 :|