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 E42B0C64E7B for ; Wed, 2 Dec 2020 16:18:28 +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 3832E2173E for ; Wed, 2 Dec 2020 16:18:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3832E2173E 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]:50898 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kkUpn-0001zp-1W for qemu-devel@archiver.kernel.org; Wed, 02 Dec 2020 11:18:27 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:35800) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kkUot-0001Y6-8M for qemu-devel@nongnu.org; Wed, 02 Dec 2020 11:17:31 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:53449) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kkUop-0003Tg-Ik for qemu-devel@nongnu.org; Wed, 02 Dec 2020 11:17:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606925845; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=xG4Bzfr2fIkqTusaxbiNihpGgZPsyogyCeYrfzC17pw=; b=jPH/bwkh+KRM3wXdx3/eoSeTsR/UyGN9PEJWzyprcM0ovtZCIGyfvTbHVI66NZz4INVrg8 sTdhUfrL70f7GjTH6pZOHkxOL49BOCd4/V7/CBkVnUm+z326nekYZfe9+phUkx7dGb1jXh AlBNCMwaus7Dg6rPHZ2OlYk9ESS1gQY= 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-199-w6XdX5n3NVuICNmQa7y6Cg-1; Wed, 02 Dec 2020 11:17:18 -0500 X-MC-Unique: w6XdX5n3NVuICNmQa7y6Cg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8A32A100E429; Wed, 2 Dec 2020 16:17:06 +0000 (UTC) Received: from redhat.com (ovpn-115-57.ams2.redhat.com [10.36.115.57]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0324F100AE48; Wed, 2 Dec 2020 16:17:01 +0000 (UTC) Date: Wed, 2 Dec 2020 16:16:59 +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: <20201202161659.GL2360260@redhat.com> References: <1605810535-51254-1-git-send-email-priyankar.jain@nutanix.com> <20201119184724.GO579364@redhat.com> <057612c5-a9b8-c7be-c710-1b635aa361be@nutanix.com> MIME-Version: 1.0 In-Reply-To: <057612c5-a9b8-c7be-c710-1b635aa361be@nutanix.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 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 Content-Transfer-Encoding: 8bit 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: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.495, 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 Wed, Dec 02, 2020 at 09:25:27PM +0530, priyankar jain wrote: > On 20/11/20 12:17 am, Daniel P. Berrangé wrote: > > 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 > > > > How does having a separate dbus daemon resolve issue (2)? If any daemon > restarts between VM power-on and migration, the dbus-vmstate object for that > VM would have to be reinitialized, no? The private dbus damon for QEMU is expected to exist for the lifetime of that QEMU process. > Secondly, on a setup with large number of VMs, having separate dbus-daemons > leads to high cummulative memory usage by dbus daemons, is it a feasible > approach to spawn a new dbus-daemon for every QEMU, given the fact that > majority of the security aspect lies with the dbus peers, apart from the > SELinux checks provided by dbus. The memory usage of a dbus daemon shouldn't be that high. A large portion of the memory footprint should be readony pages shared between all dbus procsses. The private usage should be a functional of number of clients and the message traffic. Do you have any measured figures you're concerned with ? 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 :|