Re: [libvirt] [PATCH 0/3] Emit event on lease attach/detach

On 4/16/19 1:39 AM, Cole Robinson wrote: > On 4/5/19 3:57 AM, Michal Privoznik wrote: > > Unfortunately, we can't emit VIR_DOMAIN_EVENT_ID_DEVICE_ADDED or > > VIR_DOMAIN_EVENT_ID_DEVICE_REMOVED event because that carries device > > alias within itself and leases don't have one. > > > > Hmm. I understand that <leases> aren't really devices so it doesn't have > any direct reason to give it an info structure and assign it an alias. > But that's really an argument for why they shouldn't have been a device > to begin with. I presume we did it that way to take advantage of the > existing hotplug APIs. But then adding a special purpose event seems > like going in the opposite direction. > > How invasive is it to add an 'info' bit to lease devices, allocate > aliases with the rest of qemu devices, maybe add an ADDRESS_TYPE_LEASE > or something that is just an explicit no op for the ADDRESS consumers. > My guess is it's not too bad but there could be dragons lurking > > There's already places internally where this would simplify things: it's > annoying that device iterator code already needs to play games like > 'check the address of all devices, oh except leases and graphics which > don't have info, oh and hostdev info is a pointer for some reason' Yeah, it's annoying, but I remember discussion from when I was introducing user aliases. I wanted to just have some dummy element that would not mean anything to libvirt but users could set it and then match devices using it as a mark. It was rejected because it doesn't map onto anything in qemu. Well, nor do leases, nor would their address. I don't have a preference here really. But if we wanted to invent addresees for leases then I guess we would have to do it for already running domains too (when daemon restarts).