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=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 74F5BC56201 for ; Thu, 19 Nov 2020 18:49:34 +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 D79AA24655 for ; Thu, 19 Nov 2020 18:49:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fXAMICVr" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D79AA24655 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]:42282 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kfozs-0004oI-Rl for qemu-devel@archiver.kernel.org; Thu, 19 Nov 2020 13:49:32 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:36236) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kfoyc-0003jS-U3 for qemu-devel@nongnu.org; Thu, 19 Nov 2020 13:48:14 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:40701) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kfoyb-0002nt-2r for qemu-devel@nongnu.org; Thu, 19 Nov 2020 13:48:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605811692; 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:in-reply-to:in-reply-to: references:references; bh=Q4ZOxYZ9o3i6F/GUESD02HkAzzNl3ZkBOghlYMjoQ2g=; b=fXAMICVro+cVA3+9/Mcq3XyXsk8zMOq9BkUbmtI3SU7rwqQ9PbKi2rstPi4a6CLIxk+zwg Qvc6VlcAT5OKxR9nDxCu+rorfxbaQG4cf1rd7zTXNevARg0KQvKfUPXp3DDJ1CGHVZ9FKL 0AkVvD9wCS8bDl+TLCMtWUYwABrkmCs= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-589-a1yL50BbNhynvMM9S9bxZg-1; Thu, 19 Nov 2020 13:47:33 -0500 X-MC-Unique: a1yL50BbNhynvMM9S9bxZg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3506880EFAA; Thu, 19 Nov 2020 18:47:32 +0000 (UTC) Received: from redhat.com (ovpn-114-191.ams2.redhat.com [10.36.114.191]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0954760BE2; Thu, 19 Nov 2020 18:47:27 +0000 (UTC) Date: Thu, 19 Nov 2020 18:47:24 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Priyankar Jain Subject: Re: [RFC] dbus-vmstate: Connect to the dbus only during the migration phase Message-ID: <20201119184724.GO579364@redhat.com> References: <1605810535-51254-1-git-send-email-priyankar.jain@nutanix.com> MIME-Version: 1.0 In-Reply-To: <1605810535-51254-1-git-send-email-priyankar.jain@nutanix.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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_H3=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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Peter Turschmid , qemu-devel@nongnu.org, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Raphael Norwitz Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Nov 19, 2020 at 06:28:55PM +0000, Priyankar Jain wrote: > Today, dbus-vmstate maintains a constant connection to the dbus. This is > problematic for a number of reasons: > 1. If dbus-vmstate is attached during power-on, then the device holds > the unused connection for a long period of time until migration > is triggered, thus unnecessarily occupying dbus. > 2. Similarly, if the dbus is restarted in the time period between VM > power-on (dbus-vmstate initialisation) and migration, then the > migration will fail. The only way to recover would be by > re-initialising the dbus-vmstate object. > 3. If dbus is not available during VM power-on, then currently dbus-vmstate > initialisation fails, causing power-on to fail. > 4. For a system with large number of VMs, having multiple QEMUs connected to > the same dbus can lead to a DoS for new connections. The expectation is that there is a *separate* dbus daemon created for each QEMU instance. There should never be multiple QEMUs connected to the same dbus instance, nor should it ever connect to the common dbus instances provided by most Linux distros. None of these 4 issues should apply when each QEMU has its own dedicated dbus instance AFAICT. 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 :|