On 05.04.23 19:04, Niklas Schnelle wrote: > One more question though, what about the SEID why does that have to be > fixed and at least partially match what ISM devices use? I think I'm > missing some SMC protocol/design detail here. I'm guessing this would > require a protocol change? > > Thanks, > Niklas Niklas, in the initial SMC CLC handshake the client and server exchange the SEID (one per peer system) and up to 8 proposals for SMC-D interfaces. Wen's current proposal assumes that smc-d loopback can be one of these 8 proposed interfaces, iiuc. So on s390 the proposal can contain ISM devices and a smc-d loopback device at the same time. If one of the peers is e.g. an older Linux version, it will just ignore the loopback-device in the list (Don't find a match for CHID 0xFFFF) and use an ISM interface for SMC-D if possible. Therefor it is important that the SEID is used in the same way as it is today in the handshake. If we decide for some reason (virtio-ism open issues?) that a protocol change/extension is required/wanted, then it is a new game and we can come up with new identifiers, but we may lose compatibility to backlevel systems. Alexandra
