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Wed, 5 Aug 2020 02:41:55 +0000 (UTC) Subject: Re: device compatibility interface for live migration with assigned devices To: Yan Zhao References: <20200713232957.GD5955@joy-OptiPlex-7040> <9bfa8700-91f5-ebb4-3977-6321f0487a63@redhat.com> <20200716083230.GA25316@joy-OptiPlex-7040> <20200717101258.65555978@x1.home> <20200721005113.GA10502@joy-OptiPlex-7040> <20200727072440.GA28676@joy-OptiPlex-7040> <20200727162321.7097070e@x1.home> <20200729080503.GB28676@joy-OptiPlex-7040> <20200804183503.39f56516.cohuck@redhat.com> <20200805021654.GB30485@joy-OptiPlex-7040> From: Jason Wang Message-ID: <2624b12f-3788-7e2b-2cb7-93534960bcb7@redhat.com> Date: Wed, 5 Aug 2020 10:41:54 +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: <20200805021654.GB30485@joy-OptiPlex-7040> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 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 = 2020/08/04 22:22:44 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_H4=-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: Cornelia Huck , kvm@vger.kernel.org, libvir-list@redhat.com, qemu-devel@nongnu.org, kwankhede@nvidia.com, eauger@redhat.com, xin-ran.wang@intel.com, eskultet@redhat.com, openstack-discuss@lists.openstack.org, shaohe.feng@intel.com, kevin.tian@intel.com, 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, berrange@redhat.com, corbet@lwn.net, Jiri Pirko , dinechin@redhat.com, devel@ovirt.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 2020/8/5 上午10:16, Yan Zhao wrote: > On Wed, Aug 05, 2020 at 10:22:15AM +0800, Jason Wang wrote: >> On 2020/8/5 上午12:35, Cornelia Huck wrote: >>> [sorry about not chiming in earlier] >>> >>> On Wed, 29 Jul 2020 16:05:03 +0800 >>> Yan Zhao wrote: >>> >>>> On Mon, Jul 27, 2020 at 04:23:21PM -0600, Alex Williamson wrote: >>> (...) >>> >>>>> Based on the feedback we've received, the previously proposed interface >>>>> is not viable. I think there's agreement that the user needs to be >>>>> able to parse and interpret the version information. Using json seems >>>>> viable, but I don't know if it's the best option. Is there any >>>>> precedent of markup strings returned via sysfs we could follow? >>> I don't think encoding complex information in a sysfs file is a viable >>> approach. Quoting Documentation/filesystems/sysfs.rst: >>> >>> "Attributes should be ASCII text files, preferably with only one value >>> per file. It is noted that it may not be efficient to contain only one >>> value per file, so it is socially acceptable to express an array of >>> values of the same type. >>> Mixing types, expressing multiple lines of data, and doing fancy >>> formatting of data is heavily frowned upon." >>> >>> Even though this is an older file, I think these restrictions still >>> apply. >> >> +1, that's another reason why devlink(netlink) is better. >> > hi Jason, > do you have any materials or sample code about devlink, so we can have a good > study of it? > I found some kernel docs about it but my preliminary study didn't show me the > advantage of devlink. CC Jiri and Parav for a better answer for this. My understanding is that the following advantages are obvious (as I replied in another thread): - existing users (NIC, crypto, SCSI, ib), mature and stable - much better error reporting (ext_ack other than string or errno) - namespace aware - do not couple with kobject Thanks > > Thanks > Yan >