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=-5.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 60C91C433E1 for ; Wed, 15 Jul 2020 08:23:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 32C3F20672 for ; Wed, 15 Jul 2020 08:23:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="FzHLoVeO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729679AbgGOIXb (ORCPT ); Wed, 15 Jul 2020 04:23:31 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:30279 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729652AbgGOIXb (ORCPT ); Wed, 15 Jul 2020 04:23:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1594801408; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=H1N3KvEZTGjGVeuRJgwl++MJgD0/MJqWd13En7/X0GI=; b=FzHLoVeOLAnf6bvAltvJMoWhjK1MUb2YlgXgDRogdNoizY+UrxP+whsdDRpoYuV5wW733j CYEv+/mySXraD77h9aoQwUc7YcZmcf+qsyjD7TbuJbn1sMKg5rHsgP6ukJKU+MfzDUFo7Y DW75GSYV1sDztb5cKL5xbCyAYdYHXEE= 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-393-1LaqrPl6Pga-cYMArC2aQg-1; Wed, 15 Jul 2020 04:23:26 -0400 X-MC-Unique: 1LaqrPl6Pga-cYMArC2aQg-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 6874C8014D4; Wed, 15 Jul 2020 08:23:24 +0000 (UTC) Received: from work-vm (ovpn-114-223.ams2.redhat.com [10.36.114.223]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 65E9D60BF4; Wed, 15 Jul 2020 08:23:11 +0000 (UTC) Date: Wed, 15 Jul 2020 09:23:09 +0100 From: "Dr. David Alan Gilbert" To: Alex Williamson Cc: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Yan Zhao , devel@ovirt.org, openstack-discuss@lists.openstack.org, libvir-list@redhat.com, intel-gvt-dev@lists.freedesktop.org, kvm@vger.kernel.org, qemu-devel@nongnu.org, smooney@redhat.com, eskultet@redhat.com, cohuck@redhat.com, dinechin@redhat.com, corbet@lwn.net, kwankhede@nvidia.com, eauger@redhat.com, jian-feng.ding@intel.com, hejie.xu@intel.com, kevin.tian@intel.com, zhenyuw@linux.intel.com, bao.yumeng@zte.com.cn, xin-ran.wang@intel.com, shaohe.feng@intel.com Subject: Re: device compatibility interface for live migration with assigned devices Message-ID: <20200715082309.GC2864@work-vm> References: <20200713232957.GD5955@joy-OptiPlex-7040> <20200714102129.GD25187@redhat.com> <20200714101616.5d3a9e75@x1.home> <20200714171946.GL2728@work-vm> <20200714145948.17b95eb3@x1.home> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200714145948.17b95eb3@x1.home> User-Agent: Mutt/1.14.5 (2020-06-23) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org * Alex Williamson (alex.williamson@redhat.com) wrote: > On Tue, 14 Jul 2020 18:19:46 +0100 > "Dr. David Alan Gilbert" wrote: > > > * Alex Williamson (alex.williamson@redhat.com) wrote: > > > On Tue, 14 Jul 2020 11:21:29 +0100 > > > Daniel P. Berrangé wrote: > > > > > > > On Tue, Jul 14, 2020 at 07:29:57AM +0800, Yan Zhao wrote: > > > > > hi folks, > > > > > we are defining a device migration compatibility interface that helps upper > > > > > layer stack like openstack/ovirt/libvirt to check if two devices are > > > > > live migration compatible. > > > > > The "devices" here could be MDEVs, physical devices, or hybrid of the two. > > > > > e.g. we could use it to check whether > > > > > - a src MDEV can migrate to a target MDEV, > > > > > - a src VF in SRIOV can migrate to a target VF in SRIOV, > > > > > - a src MDEV can migration to a target VF in SRIOV. > > > > > (e.g. SIOV/SRIOV backward compatibility case) > > > > > > > > > > The upper layer stack could use this interface as the last step to check > > > > > if one device is able to migrate to another device before triggering a real > > > > > live migration procedure. > > > > > we are not sure if this interface is of value or help to you. please don't > > > > > hesitate to drop your valuable comments. > > > > > > > > > > > > > > > (1) interface definition > > > > > The interface is defined in below way: > > > > > > > > > > __ userspace > > > > > /\ \ > > > > > / \write > > > > > / read \ > > > > > ________/__________ ___\|/_____________ > > > > > | migration_version | | migration_version |-->check migration > > > > > --------------------- --------------------- compatibility > > > > > device A device B > > > > > > > > > > > > > > > a device attribute named migration_version is defined under each device's > > > > > sysfs node. e.g. (/sys/bus/pci/devices/0000\:00\:02.0/$mdev_UUID/migration_version). > > > > > userspace tools read the migration_version as a string from the source device, > > > > > and write it to the migration_version sysfs attribute in the target device. > > > > > > > > > > The userspace should treat ANY of below conditions as two devices not compatible: > > > > > - any one of the two devices does not have a migration_version attribute > > > > > - error when reading from migration_version attribute of one device > > > > > - error when writing migration_version string of one device to > > > > > migration_version attribute of the other device > > > > > > > > > > The string read from migration_version attribute is defined by device vendor > > > > > driver and is completely opaque to the userspace. > > > > > for a Intel vGPU, string format can be defined like > > > > > "parent device PCI ID" + "version of gvt driver" + "mdev type" + "aggregator count". > > > > > > > > > > for an NVMe VF connecting to a remote storage. it could be > > > > > "PCI ID" + "driver version" + "configured remote storage URL" > > > > > > > > > > for a QAT VF, it may be > > > > > "PCI ID" + "driver version" + "supported encryption set". > > > > > > > > > > (to avoid namespace confliction from each vendor, we may prefix a driver name to > > > > > each migration_version string. e.g. i915-v1-8086-591d-i915-GVTg_V5_8-1) > > > > > > It's very strange to define it as opaque and then proceed to describe > > > the contents of that opaque string. The point is that its contents > > > are defined by the vendor driver to describe the device, driver version, > > > and possibly metadata about the configuration of the device. One > > > instance of a device might generate a different string from another. > > > The string that a device produces is not necessarily the only string > > > the vendor driver will accept, for example the driver might support > > > backwards compatible migrations. > > > > (As I've said in the previous discussion, off one of the patch series) > > > > My view is it makes sense to have a half-way house on the opaqueness of > > this string; I'd expect to have an ID and version that are human > > readable, maybe a device ID/name that's human interpretable and then a > > bunch of other cruft that maybe device/vendor/version specific. > > > > I'm thinking that we want to be able to report problems and include the > > string and the user to be able to easily identify the device that was > > complaining and notice a difference in versions, and perhaps also use > > it in compatibility patterns to find compatible hosts; but that does > > get tricky when it's a 'ask the device if it's compatible'. > > In the reply I just sent to Dan, I gave this example of what a > "compatibility string" might look like represented as json: > > { > "device_api": "vfio-pci", > "vendor": "vendor-driver-name", > "version": { > "major": 0, > "minor": 1 > }, > "vfio-pci": { // Based on above device_api > "vendor": 0x1234, // Values for the exposed device > "device": 0x5678, > // Possibly further parameters for a more specific match > }, > "mdev_attrs": [ > { "attribute0": "VALUE" } > ] > } > > Are you thinking that we might allow the vendor to include a vendor > specific array where we'd simply require that both sides have matching > fields and values? ie. > > "vendor_fields": [ > { "unknown_field0": "unknown_value0" }, > { "unknown_field1": "unknown_value1" }, > ] > > We could certainly make that part of the spec, but I can't really > figure the value of it other than to severely restrict compatibility, > which the vendor could already do via the version.major value. Maybe > they'd want to put a build timestamp, random uuid, or source sha1 into > such a field to make absolutely certain compatibility is only determined > between identical builds? Thanks, No, I'd mostly anticipated matching on the vendor and device and maybe a version number for the bit the user specifies; I had assumed all that 'vendor cruft' was still mostly opaque; having said that, if it did become a list of attributes like that (some of which were vendor specific) that would make sense to me. Dave > > Alex -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK