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Wed, 19 Aug 2020 02:38:14 +0000 (UTC) Subject: Re: device compatibility interface for live migration with assigned devices To: =?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> From: Jason Wang Message-ID: <5aea4ae6-e8c8-1120-453d-20a78cee6b20@redhat.com> Date: Wed, 19 Aug 2020 10:38:13 +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: <20200818091628.GC20215@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 10.5.11.15 Received-SPF: pass client-ip=207.211.31.120; envelope-from=jasowang@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/18 22:38:38 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 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_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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 , eskultet@redhat.com, smooney@redhat.com, intel-gvt-dev@lists.freedesktop.org, Cornelia Huck , 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5:16, Daniel P. Berrangé wrote: > Your mail came through as HTML-only so all the quoting and attribution > is mangled / lost now :-( My bad, sorry. > > 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 >> >> 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. > > 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. Ok, I agree with you. Thanks > > Regards, > Daniel