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=-2.4 required=3.0 tests=FROM_EXCESS_BASE64, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT 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 13035C04AAF for ; Tue, 21 May 2019 08:39:35 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D04B22173C for ; Tue, 21 May 2019 08:39:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D04B22173C 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 ([127.0.0.1]:48913 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hT0J4-0001Te-5O for qemu-devel@archiver.kernel.org; Tue, 21 May 2019 04:39:34 -0400 Received: from eggs.gnu.org ([209.51.188.92]:47218) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hT0H6-0000bC-Ml for qemu-devel@nongnu.org; Tue, 21 May 2019 04:37:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hT0H5-0005hu-9G for qemu-devel@nongnu.org; Tue, 21 May 2019 04:37:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39496) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hT0H5-0005hI-1i for qemu-devel@nongnu.org; Tue, 21 May 2019 04:37:31 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A350F356E7 for ; Tue, 21 May 2019 08:37:19 +0000 (UTC) Received: from redhat.com (ovpn-112-26.ams2.redhat.com [10.36.112.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CCF92176C9; Tue, 21 May 2019 08:37:10 +0000 (UTC) Date: Tue, 21 May 2019 09:37:07 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Jens Freimann Message-ID: <20190521083707.GE25835@redhat.com> References: <20190517125820.2885-1-jfreimann@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190517125820.2885-1-jfreimann@redhat.com> User-Agent: Mutt/1.11.4 (2019-03-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Tue, 21 May 2019 08:37:24 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 0/4] add failover feature for assigned network devices X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: pkrempa@redhat.com, ehabkost@redhat.com, mst@redhat.com, aadam@redhat.com, qemu-devel@nongnu.org, laine@redhat.com, ailan@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, May 17, 2019 at 02:58:16PM +0200, Jens Freimann wrote: > This is another attempt at implementing the host side of the > net_failover concept > (https://www.kernel.org/doc/html/latest/networking/net_failover.html) > > Changes since last RFC: > - work around circular dependency of commandline options. Just add > failover=on to the virtio-net standby options and reference it from > primary (vfio-pci) device with standby= > - add patch 3/4 to allow migration of vfio-pci device when it is part of a > failover pair, still disallow for all other devices > - add patch 4/4 to allow unplug of device during migrationm, make an > exception for failover primary devices. I'd like feedback on how to > solve this more elegant. I added a boolean to DeviceState, have it > default to false for all devices except for primary devices. > - not tested yet with surprise removal > - I don't expect this to go in as it is, still needs more testing but > I'd like to get feedback on above mentioned changes. > > The general idea is that we have a pair of devices, a vfio-pci and a > emulated device. Before migration the vfio device is unplugged and data > flows to the emulated device, on the target side another vfio-pci device > is plugged in to take over the data-path. In the guest the net_failover > module will pair net devices with the same MAC address. > > * In the first patch the infrastructure for hiding the device is added > for the qbus and qdev APIs. > > * In the second patch the virtio-net uses the API to defer adding the vfio > device until the VIRTIO_NET_F_STANDBY feature is acked. > > Previous discussion: > RFC v1 https://patchwork.ozlabs.org/cover/989098/ > RFC v2 https://www.mail-archive.com/qemu-devel@nongnu.org/msg606906.html > > To summarize concerns/feedback from previous discussion: > 1.- guest OS can reject or worse _delay_ unplug by any amount of time. > Migration might get stuck for unpredictable time with unclear reason. > This approach combines two tricky things, hot/unplug and migration. > -> We can surprise-remove the PCI device and in QEMU we can do all > necessary rollbacks transparent to management software. Will it be > easy, probably not. > 2. PCI devices are a precious ressource. The primary device should never > be added to QEMU if it won't be used by guest instead of hiding it in > QEMU. > -> We only hotplug the device when the standby feature bit was > negotiated. We save the device cmdline options until we need it for > qdev_device_add() > Hiding a device can be a useful concept to model. For example a > pci device in a powered-off slot could be marked as hidden until the slot is > powered on (mst). > 3. Management layer software should handle this. Open Stack already has > components/code to handle unplug/replug VFIO devices and metadata to > provide to the guest for detecting which devices should be paired. > -> An approach that includes all software from firmware to > higher-level management software wasn't tried in the last years. This is > an attempt to keep it simple and contained in QEMU as much as possible. > 4. Hotplugging a device and then making it part of a failover setup is > not possible > -> addressed by extending qdev hotplug functions to check for hidden > attribute, so e.g. device_add can be used to plug a device. > > > I have tested this with a mlx5 NIC and was able to migrate the VM with > above mentioned workarounds for open problems. > > Command line example: > > qemu-system-x86_64 -enable-kvm -m 3072 -smp 3 \ > -machine q35,kernel-irqchip=split -cpu host \ > -k fr \ > -serial stdio \ > -net none \ > -qmp unix:/tmp/qmp.socket,server,nowait \ > -monitor telnet:127.0.0.1:5555,server,nowait \ > -device pcie-root-port,id=root0,multifunction=on,chassis=0,addr=0xa \ > -device pcie-root-port,id=root1,bus=pcie.0,chassis=1 \ > -device pcie-root-port,id=root2,bus=pcie.0,chassis=2 \ > -netdev tap,script=/root/bin/bridge.sh,downscript=no,id=hostnet1,vhost=on \ > -device virtio-net-pci,netdev=hostnet1,id=net1,mac=52:54:00:6f:55:cc,bus=root2,failover=on \ > /root/rhel-guest-image-8.0-1781.x86_64.qcow2 > > Then the primary device can be hotplugged via > (qemu) device_add vfio-pci,host=5e:00.2,id=hostdev0,bus=root1,standby=net1 This command line syntax looks much saner now that the circular dep is gone. I think this approach is now viable to use from libvirt's POV. 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 :|