Re: [Qemu-devel] [PATCH v5 0/3] virtio-scsi: restart DMA after iothread

[Paolo Bonzini]

On 20/06/19 19:37, Stefan Hajnoczi wrote:
> v5:
>  * Plumbing vm change state handlers into DeviceClass/BusClass is a rather
>    large bug fix.  Instead I've combined the previous priorities approach with
>    the observation from Kevin and Paolo that we really want to order by qdev
>    tree depth.
> 
>    The new qdev_add_vm_change_state_handler() API lets DeviceStates register
>    callbacks that execute in qdev tree depth order.  This solves the
>    virtio-scsi bug since the virtio-scsi device's callback must complete 
> before
>    its child scsi-disk's callback runs.
> 
>    Is this a good compromise for everyone?

Yes!  Perhaps a bit of a hack, but it works and both the API and the
implementation are very sane.  Converting other devices to use
qdev_add_vm_change_state_handler() is left as an exercise for the
reviewer, I guess? :)

Paolo