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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_HK_NAME_DR,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 D8BDEC04AB6 for ; Fri, 31 May 2019 18:46:46 +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 A9DF326E15 for ; Fri, 31 May 2019 18:46:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A9DF326E15 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]:47740 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hWmY9-0006Fn-V1 for qemu-devel@archiver.kernel.org; Fri, 31 May 2019 14:46:45 -0400 Received: from eggs.gnu.org ([209.51.188.92]:37809) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hWmWu-0005g2-LC for qemu-devel@nongnu.org; Fri, 31 May 2019 14:45:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hWmWt-0007wM-G6 for qemu-devel@nongnu.org; Fri, 31 May 2019 14:45:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56514) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hWmWt-0007qh-7V for qemu-devel@nongnu.org; Fri, 31 May 2019 14:45:27 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0642880B49 for ; Fri, 31 May 2019 18:45:26 +0000 (UTC) Received: from work-vm (ovpn-117-254.ams2.redhat.com [10.36.117.254]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3A1B35DE81; Fri, 31 May 2019 18:45:15 +0000 (UTC) Date: Fri, 31 May 2019 19:45:13 +0100 From: "Dr. David Alan Gilbert" To: "Michael S. Tsirkin" Message-ID: <20190531184512.GN3169@work-vm> References: <20190517125820.2885-4-jfreimann@redhat.com> <20190521094504.GB2915@work-vm> <20190530145645.tjwkgi4hae5yblsi@jenstp.localdomain> <20190530134631-mutt-send-email-mst@kernel.org> <20190530180022.GB2864@work-vm> <20190530140419-mutt-send-email-mst@kernel.org> <20190530182210.GA22103@habkost.net> <20190530190322-mutt-send-email-mst@kernel.org> <20190531170154.GB22103@habkost.net> <20190531135059-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190531135059-mutt-send-email-mst@kernel.org> User-Agent: Mutt/1.11.4 (2019-03-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Fri, 31 May 2019 18:45:26 +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 3/4] net/virtio: add failover support 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: , Cc: pkrempa@redhat.com, berrange@redhat.com, Eduardo Habkost , aadam@redhat.com, qemu-devel@nongnu.org, laine@redhat.com, jdenemar@redhat.com, Jens Freimann , ailan@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Michael S. Tsirkin (mst@redhat.com) wrote: > On Fri, May 31, 2019 at 02:01:54PM -0300, Eduardo Habkost wrote: > > > Yes. It's just lots of extremely low level interfaces > > > and all rather pointless. > > > > > > And down the road extensions like surprise removal support will make it > > > all cleaner and more transparent. Floating things up to libvirt means > > > all these low level details will require more and more hacks. > > > > Why do you call it pointless? > > We'd need APIs to manipulate device visibility to guest, hotplug > controller state and separately manipulate the resources allocated. This > is low level stuff that users really have no idea what to do about. > Exposing such a level of detail to management is imho pointless. > We are better off with a high level API, see below. so I don't know much about vfio; but to me it strikes me that you wouldn't need that low level detail if we just reworked vfio to look more like all our other devices; something like: -vfiodev host=02:00.0,id=gpu -device vfio-pci,dev=gpu The 'vfiodev' would own the resources; so to do this trick, the management layer would: hotunplug the vfio-pci migrate if anything went wrong it would hotplug the vfio-pci backin you wouldn't have free'd up any resources because they belonged to the vfiodev. > > If we want this to work before > > surprise removal is implemented, we need to provide an API that > > works for management software. > > Don't we want to make this work > > without surprise removal too? > > This patchset adds an optional, off by default support for > migrating guests with an assigned network device. > If enabled this requires guest to allow migration. > > Of course this can be viewed as a security problem since it allows guest > to block migration. We can't detect a malicious guest reliably imho. > What we can do is report to management when guest allows migration. > Policy such what to do when this does not happen for a while and > what timeout to set would be up to management. > > The API in question would be a high level one, something > along the lines of a single "guest allowed migration" event. This is all fairly normal problems with hot unplugging - that's already dealt with at higher levels for normal hot unplugging. The question here is to try to avoid duplicating that fairly painful process in qemu. Dave > > -- > MST -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK