On Mon, 2019-09-09 at 08:41 -0400, Michael S. Tsirkin wrote: > > The only thing we could do is crash if it wants to use this feature > > without the others, but would that really be helpful? > > We can return failure from SET_PROTOCOL_FEATURES. > We can also fail all following messages.
Only if we have F_REPLY_ACK, I think? I suppose we could fail a later command that already needs a reply without REPLY_ACK, but that seems difficult to debug? Anyway, if you feel that we should have this as some sort of safeguard I can try to do that; to me it feels rather pointless as libvhost-user is more of a sample implementation than anything else. Unless you also wanted to write into the spec that F_KICK_CALL_MSGS absolutely *requires* F_REPLY_ACK, and add some text that tells a device how to behave when F_KICK_CALL_MSGS is negotiated without F_REPLY_ACK? johannes
