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=-8.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, 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 EC873C433DF for ; Wed, 19 Aug 2020 02:55:09 +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 B36702076E for ; Wed, 19 Aug 2020 02:55:09 +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="dcpQHrdj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B36702076E 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]:57354 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1k8EFp-0005n4-1K for qemu-devel@archiver.kernel.org; Tue, 18 Aug 2020 22:55:09 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48952) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1k8EFH-0005NQ-Gm for qemu-devel@nongnu.org; Tue, 18 Aug 2020 22:54:35 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:30908 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1k8EFF-0008TD-N4 for qemu-devel@nongnu.org; Tue, 18 Aug 2020 22:54:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1597805672; 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=OyfXHDOh3tadbBcQyUmurCPsA+lHPesiQMeXAJCp/nc=; b=dcpQHrdjp17Mw2qkMauO5Q20k1w9svhtM7bKfvmSfkbXPpdv/JnC1cbJ8i7l/X+f4Kouux IT8s+z7g2+S5F0hA1rI5/Yh3iEoqpwoEUFHLLT/AiICOd/mjC9G/T6Y3x4skwYxlllUFSU g6Vbe66q1f1qQgn+9b9mmij7uSY1qIM= 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-207-Ay-EfPfqMQ6MMOO5kbt_wg-1; Tue, 18 Aug 2020 22:54:29 -0400 X-MC-Unique: Ay-EfPfqMQ6MMOO5kbt_wg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7656381F030; Wed, 19 Aug 2020 02:54:26 +0000 (UTC) Received: from [10.72.13.88] (ovpn-13-88.pek2.redhat.com [10.72.13.88]) by smtp.corp.redhat.com (Postfix) with ESMTP id D15481B47B; Wed, 19 Aug 2020 02:54:08 +0000 (UTC) Subject: Re: device compatibility interface for live migration with assigned devices To: Cornelia Huck , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= References: <20200805075647.GB2177@nanopsycho> <20200805093338.GC30485@joy-OptiPlex-7040> <20200805105319.GF2177@nanopsycho> <20200810074631.GA29059@joy-OptiPlex-7040> <20200814051601.GD15344@joy-OptiPlex-7040> <20200818085527.GB20215@redhat.com> <3a073222-dcfe-c02d-198b-29f6a507b2e1@redhat.com> <20200818091628.GC20215@redhat.com> <20200818113652.5d81a392.cohuck@redhat.com> From: Jason Wang Message-ID: Date: Wed, 19 Aug 2020 10:54:07 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200818113652.5d81a392.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Received-SPF: pass client-ip=207.211.31.81; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/18 22:46:24 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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_H2=-1, 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: , Cc: kvm@vger.kernel.org, libvir-list@redhat.com, qemu-devel@nongnu.org, kwankhede@nvidia.com, eauger@redhat.com, xin-ran.wang@intel.com, corbet@lwn.net, openstack-discuss@lists.openstack.org, shaohe.feng@intel.com, kevin.tian@intel.com, Yan Zhao , Parav Pandit , jian-feng.ding@intel.com, dgilbert@redhat.com, zhenyuw@linux.intel.com, hejie.xu@intel.com, bao.yumeng@zte.com.cn, Alex Williamson , smooney@redhat.com, intel-gvt-dev@lists.freedesktop.org, eskultet@redhat.com, Jiri Pirko , dinechin@redhat.com, devel@ovirt.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020/8/18 下午5:36, Cornelia Huck wrote: > On Tue, 18 Aug 2020 10:16:28 +0100 > Daniel P. Berrangé wrote: > >> On Tue, Aug 18, 2020 at 05:01:51PM +0800, Jason Wang wrote: >>> On 2020/8/18 下午4:55, Daniel P. Berrangé wrote: >>> >>> On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote: >>> >>> On 2020/8/14 下午1:16, Yan Zhao wrote: >>> >>> On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote: >>> >>> On 2020/8/10 下午3:46, Yan Zhao wrote: >>> we actually can also retrieve the same information through sysfs, .e.g >>> >>> |- [path to device] >>> |--- migration >>> | |--- self >>> | | |---device_api >>> | | |---mdev_type >>> | | |---software_version >>> | | |---device_id >>> | | |---aggregator >>> | |--- compatible >>> | | |---device_api >>> | | |---mdev_type >>> | | |---software_version >>> | | |---device_id >>> | | |---aggregator >>> >>> >>> Yes but: >>> >>> - You need one file per attribute (one syscall for one attribute) >>> - Attribute is coupled with kobject > Is that really that bad? You have the device with an embedded kobject > anyway, and you can just put things into an attribute group? Yes, but all of this could be done via devlink(netlink) as well with low overhead. > > [Also, I think that self/compatible split in the example makes things > needlessly complex. Shouldn't semantic versioning and matching already > cover nearly everything? That's my question as well. E.g for virtio, versioning may not even work, some of features are negotiated independently: Source features: A, B, C Dest features: A, B, C, E We just need to make sure the dest features is a superset of source then all set. > I would expect very few cases that are more > complex than that. Maybe the aggregation stuff, but I don't think we > need that self/compatible split for that, either.] > >>> All of above seems unnecessary. >>> >>> Another point, as we discussed in another thread, it's really hard to make >>> sure the above API work for all types of devices and frameworks. So having a >>> vendor specific API looks much better. >>> >>> From the POV of userspace mgmt apps doing device compat checking / migration, >>> we certainly do NOT want to use different vendor specific APIs. We want to >>> have an API that can be used / controlled in a standard manner across vendors. >>> >>> Yes, but it could be hard. E.g vDPA will chose to use devlink (there's a >>> long debate on sysfs vs devlink). So if we go with sysfs, at least two >>> APIs needs to be supported ... >> NB, I was not questioning devlink vs sysfs directly. If devlink is related >> to netlink, I can't say I'm enthusiastic as IMKE sysfs is easier to deal >> with. I don't know enough about devlink to have much of an opinion though. >> The key point was that I don't want the userspace APIs we need to deal with >> to be vendor specific. > From what I've seen of devlink, it seems quite nice; but I understand > why sysfs might be easier to deal with (especially as there's likely > already a lot of code using it.) > > I understand that some users would like devlink because it is already > widely used for network drivers (and some others), but I don't think > the majority of devices used with vfio are network (although certainly > a lot of them are.) Note that though devlink could be popular only in network devices, netlink is widely used by a lot of subsystesm (e.g SCSI). Thanks > >> What I care about is that we have a *standard* userspace API for performing >> device compatibility checking / state migration, for use by QEMU/libvirt/ >> OpenStack, such that we can write code without countless vendor specific >> code paths. >> >> If there is vendor specific stuff on the side, that's fine as we can ignore >> that, but the core functionality for device compat / migration needs to be >> standardized. > To summarize: > - choose one of sysfs or devlink > - have a common interface, with a standardized way to add > vendor-specific attributes > ?