On 2011-12-05 13:36, Avi Kivity wrote: > On 12/05/2011 01:37 PM, Jan Kiszka wrote: >> On 2011-12-05 11:01, Avi Kivity wrote: >>> On 12/04/2011 11:38 PM, Jan Kiszka wrote: >>>>> >>>>> It should be also possible to migrate from non-KVM device to KVM >>>>> version, different names would prevent that for ever. >>>> >>>> It is (theoretically) possible with these patches as the vmstate names >>>> are the same. KVM to TCG migration does not work right now, so I was >>>> only able to test in-kernel <-> user space irqchip model migrations. >>> >>> btw, for the next-gen migration protocol, we'd probably be using QOM >>> paths, not vmstate names; the QOM paths would include the device name? >> >> That would be a very bad idea IMHO. Every refactoring of your device >> tree, e.g. to model CPU hotplug and the ICC bus more accurately, would >> risk to create a migration crack. > > At some point, something has to be stable. We can't have an infinite > number of layers giving names to things. I propose we have just one layer. > >> At least we would need some stable >> naming and/or alias concept then. > > We should be able to transform a path to backward compatible names, > yes. But if something has an unstable name, let's omit it in the first > place. > > (the memory API added unstable names, hopefully the QOM can take over > the stable ones and we'll have a good way to denote the unstable ones). > OK, maybe - or likely - we should make those device models have the same names in QOM once instantiated. But I'm still convinced they should remain separated models in contrast to a single model with a property. The kvm ioapic, e.g., requires an additional property (gsi_base) that is meaningless for user space devices. And its interrupts have to be wired&configured differently at board model level. So, from the QEMU POV, it is a very different device. Just the guest does not notice. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
