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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 43F0AC77B7E for ; Thu, 25 May 2023 09:33:58 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1q27LS-00067y-SS; Thu, 25 May 2023 05:33:18 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q27LR-00067m-6u for qemu-devel@nongnu.org; Thu, 25 May 2023 05:33:17 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1q27LP-00056h-2C for qemu-devel@nongnu.org; Thu, 25 May 2023 05:33:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1685007193; h=from:from: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=DZIEimjz+ttg394lY3rDlCId4IhIo68BzUhyhEUeTHA=; b=hL1bmIe/jhEaksvhzhdrRUE439mho/cBCBX7JesQsGBSvTS9bIano4jXluOQ8N2ZBtcXE2 zOgYadh5l+pD+erMVI82/9kJKoJu6C8DSUHsr4Z1cyOBIBjg/Cn5vcmgxNF0nDzgEMPHIT B56izJ4c0tqtncsOMtZgIbo5Ov8JWm8= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-663-7pc0vlW0MGO5bdntgTvWgA-1; Thu, 25 May 2023 05:33:10 -0400 X-MC-Unique: 7pc0vlW0MGO5bdntgTvWgA-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 62B90185A78E; Thu, 25 May 2023 09:33:09 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.91]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 37894492B00; Thu, 25 May 2023 09:33:09 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 263B521E692E; Thu, 25 May 2023 11:33:08 +0200 (CEST) From: Markus Armbruster To: Avihai Horon Cc: , Alex Williamson , =?utf-8?Q?C=C3=A9dric?= Le Goater , Eduardo Habkost , Marcel Apfelbaum , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Yanan Wang , Juan Quintela , Peter Xu , Leonardo Bras , Eric Blake , Thomas Huth , Laurent Vivier , Paolo Bonzini , Yishai Hadas , Jason Gunthorpe , Maor Gottlieb , Kirti Wankhede , Tarun Gupta , Joao Martins Subject: Re: [PATCH v3 1/7] migration: Add switchover ack capability References: <20230521151808.24804-1-avihaih@nvidia.com> <20230521151808.24804-2-avihaih@nvidia.com> Date: Thu, 25 May 2023 11:33:08 +0200 In-Reply-To: <20230521151808.24804-2-avihaih@nvidia.com> (Avihai Horon's message of "Sun, 21 May 2023 18:18:02 +0300") Message-ID: <87edn4u563.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@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, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Avihai Horon writes: > Migration downtime estimation is calculated based on bandwidth and > remaining migration data. This assumes that loading of migration data in > the destination takes a negligible amount of time and that downtime > depends only on network speed. > > While this may be true for RAM, it's not necessarily true for other > migration users. For example, loading the data of a VFIO device in the > destination might require from the device to allocate resources, prepare > internal data structures and so on. These operations can take a > significant amount of time which can increase migration downtime. > > This patch adds a new capability "switchover ack" that prevents the > source from stopping the VM and completing the migration until an ACK > is received from the destination that it's OK to do so. > > This can be used by migrated devices in various ways to reduce downtime. > For example, a device can send initial precopy metadata to pre-allocate > resources in the destination and use this capability to make sure that > the pre-allocation is completed before the source VM is stopped, so it > will have full effect. > > This new capability relies on the return path capability to communicate > from the destination back to the source. > > The actual implementation of the capability will be added in the > following patches. > > Signed-off-by: Avihai Horon QAPI schema Acked-by: Markus Armbruster