On Mon, 2020-07-20 at 11:41 +0800, Jason Wang wrote: > On 2020/7/18 上午12:12, Alex Williamson wrote: > > On Thu, 16 Jul 2020 16:32:30 +0800 > > Yan Zhao <yan.y.zhao@xxxxxxxxx> wrote: > > > > > On Thu, Jul 16, 2020 at 12:16:26PM +0800, Jason Wang wrote: > > > > On 2020/7/14 上午7:29, 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). > > > > > > > > Are you aware of the devlink based device management interface that is > > > > proposed upstream? I think it has many advantages over sysfs, do you > > > > consider to switch to that? > > > > Advantages, such as? > > > My understanding for devlink(netlink) over sysfs (some are mentioned at > the time of vDPA sysfs mgmt API discussion) are: i tought netlink was used more a as a configuration protocoal to qurry and confire nic and i guess other devices in its devlink form requireint a tool to be witten that can speak the protocal to interact with. the primary advantate of sysfs is that everything is just a file. there are no addtional depleenceis needed and unlike netlink there are not interoperatblity issues in a coanitnerised env. if you are using diffrenet version of libc and gcc in the contaienr vs the host my understanding is tools like ethtool from ubuntu deployed in a container on a centos host can have issue communicating with the host kernel. if its jsut a file unless the format the data is returnin in chagnes or the layout of sysfs changes its compatiable regardless of what you use to read it. > > - 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 >
