On 20 April 2015 at 15:08, Cornelia Huck <cornelia.h...@de.ibm.com> wrote: > Hmm... isn't ->plugged() called after ->realize()? > > Maybe I'm just confused, so let's try to understand the callchain :) > > VirtIONetCcw is realized > -> feature bits are used > -> embedded VirtIODevice is realized > -> VirtioCcwDevice is realized > -> features are populated > > My understanding was that ->plugged() happened after step 3, but > re-reading, it might already happen after step 2... very confusing. > (This still would be too late for the feature bits, and we don't set up > the parent bus before step 2.)
plugged gets called when the virtio backend device is realized (from the hw/virtio/virtio.c base class realize method). For virtio-ccw, your virtio_ccw_net_realize function does this (by setting the 'realized' property on the backend vdev to true). Since it does this before it calls virtio_ccw_device_realize() you get the ordering: * virtio_ccw_net_realize early stuff * virtio-net backend realize * virtio_ccw plugged method called (if you had one) * virtio_ccw_device_realize called (manually by the subclass) That's probably not a very helpful order... > virtio-pci might be slightly different due to a different topology, I > think. virtio-pci has three differences: (1) its generic 'virtio_pci_realize' is a method on a common base class, which then invokes the subclass realize (rather than having the subclass realize call the parent realize function as virtio-ccw does) (2) it implements a plugged method and a lot of work is done there (3) the virtio_net_pci_realize realizes the backend as its final action, not in the middle of doing other things So the order here is: * virtio_pci_realize (as base class realize method) * virtio_net_pci_realize * virtio-net backend realize * virtio_pci plugged method called > I'm not opposed to moving setting up the features into ->plugged(), but > I'm not sure it helps. Conceptually I think if you have code which relies on the backend existing, it is better placed in the plugged() method rather than trying to implement the realize method as a sort of two-stage thing with the backend-realize done in the middle and manual calls from the subclass back into the base class done afterwards. You can probably fix the specific weirdnesses here by being a bit more careful about what all the virtio_ccw_net_realize &c functions do before realizing the backend and what they do afterwards. But it might be long term cleaner to structure things like virtio-pci. thanks -- PMM
