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=-0.3 required=3.0 tests=DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 084CCC2BA17 for ; Mon, 6 Apr 2020 17:32:03 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 CEA7020672 for ; Mon, 6 Apr 2020 17:32:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="q7Vu5Mbn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CEA7020672 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jLVbB-0001EI-3U; Mon, 06 Apr 2020 17:31:49 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jLVb9-0001ED-Vq for xen-devel@lists.xen.org; Mon, 06 Apr 2020 17:31:48 +0000 X-Inumbo-ID: 7d90057a-782c-11ea-9e09-bc764e2007e4 Received: from mail-wm1-x343.google.com (unknown [2a00:1450:4864:20::343]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 7d90057a-782c-11ea-9e09-bc764e2007e4; Mon, 06 Apr 2020 17:31:47 +0000 (UTC) Received: by mail-wm1-x343.google.com with SMTP id j19so166986wmi.2 for ; Mon, 06 Apr 2020 10:31:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=QtQEmnvIRNjTWAGtotK8vr5aL1WEPMTRa/UAOoQ/pSk=; b=q7Vu5MbnAyAdq/X/v95seSyLeDOQk8rxYf+a67Xnw4wEm5iwv2I9i+vchjZoNsEHgD du9Y9hb9L/kmiuRzQaWSv2efPtKcOoTFKkuVfmzR4uFlEHCVI3geAXV/w/G7F7Nr+yax U5FSg0SxRBKqOQhmPv/MoQxkm9nRYLlYhfgCFO0UDFKkLA+aRro7pRIbqxASFisOATFh 0yNIeDS7PY7mYo4r+ZHcSgJcZtY6sbKvTcQ/GSrtkiCmZh0EVubXhadxbImZoxKfB44c qdDTY2AUETLxAWoincuEiBYClnfsjOg2BnKQigVyOgByxLgiDzJJ+BXHb6uzqQyHGI/2 ZQOA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=QtQEmnvIRNjTWAGtotK8vr5aL1WEPMTRa/UAOoQ/pSk=; b=ATXo26cFknS9/jxheynSbV/DGAbt6w14G4B/zr9lBdf+X6gjubRFdu3ixxkP8/SFOa 1p9hF/j7PAukkwjmADJU0/D28BbSdDvyG9KbhccCuPLoeFTm1DdRcWhODP2MG142t+m6 Hk/HpYbwQxBU/0RyJq3JSVjc4MVcmipve3BfHmkNTMo3jqlGnEyD+ZnNEVhnbpwclws+ DHkM5JJ1VJEOCb1FuMq/V3bFgSyC7YZMuU++gXiwU5M/KltwGviOdIW+oiqkT3rgbSbB pL37Ys/2dVwTKuKaMoFfZgVCk64TD0vlxAFSmZCHYc6wSxMwhiSGyJ0Ipb3XqwSh8loD 202g== X-Gm-Message-State: AGi0PuYCN5niYOOmx5mvpcuhXdXBuVyw5EJn9czqdWcfP4cLH9JLGLrx r11QQMtGc8k3VvBYFKtSXhpq2pKEvSmKSzkr004= X-Google-Smtp-Source: APiQypIbzVcQhtuKPx/sWYXqksN+tCLZDAk0hzlSjQiNX5GtwWG/GDjtfexjX56TkPBmMZS9LXKn4lmLqLhrYWNb/MQ= X-Received: by 2002:a7b:c842:: with SMTP id c2mr457489wml.154.1586194306477; Mon, 06 Apr 2020 10:31:46 -0700 (PDT) MIME-Version: 1.0 References: <6bb7eb58-01c6-00e4-672e-83d5fcb87ea0@citrix.com> In-Reply-To: <6bb7eb58-01c6-00e4-672e-83d5fcb87ea0@citrix.com> From: Tamas K Lengyel Date: Mon, 6 Apr 2020 11:31:10 -0600 Message-ID: Subject: Re: Live migration and PV device handling To: Andrew Cooper Content-Type: text/plain; charset="UTF-8" X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Xen-devel , Anastassios Nanos Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On Mon, Apr 6, 2020 at 11:24 AM Andrew Cooper wrote: > > On 06/04/2020 18:16, Tamas K Lengyel wrote: > > On Fri, Apr 3, 2020 at 6:44 AM Andrew Cooper wrote: > >> On 03/04/2020 13:32, Anastassios Nanos wrote: > >>> Hi all, > >>> > >>> I am trying to understand how live-migration happens in xen. I am > >>> looking in the HVM guest case and I have dug into the relevant parts > >>> of the toolstack and the hypervisor regarding memory, vCPU context > >>> etc. > >>> > >>> In particular, I am interested in how PV device migration happens. I > >>> assume that the guest is not aware of any suspend/resume operations > >>> being done > >> Sadly, this assumption is not correct. HVM guests with PV drivers > >> currently have to be aware in exactly the same way as PV guests. > >> > >> Work is in progress to try and address this. See > >> https://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=775a02452ddf3a6889690de90b1a94eb29c3c732 > >> (sorry - for some reason that doc isn't being rendered properly in > >> https://xenbits.xen.org/docs/ ) > > That proposal is very interesting - first time it came across my radar > > - but I dislike the idea that domain IDs need to be preserved for > > uncooperative migration to work. > > The above restriction is necessary to work with existing guests, which > is an implementation requirement of the folks driving the work. > > > Ideally I would be able to take > > advantage of the same plumbing to perform forking of VMs with PV > > drivers where preserving the domain id is impossible since its still > > in use. > > We would of course like to make changes to remove the above restriction > in the longterm. The problem is that it is not a trivial thing to fix. > Various things were discussed in Chicago, but I don't recall if any of > the plans made their way onto xen-devel. Yea I imagine trying to get this to work with existing PV drivers is not possible in any other way. But if we can update the PV driver code such that in the longterm it can work without preserving the domain ID, that would be worthwhile. Tamas