Re: [Qemu-devel] [PATCH RFC] qdev: add init order filter

[Paolo Bonzini <pbonzini@redhat.com>]

On 09/03/2017 00:59, Michael S. Tsirkin wrote:
> Allow forcing a specific order of initialization on
> devices created with -device.
> Helpful e.g. for built-in devices such as IOMMUs which must
> exist before all other devices.
> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> 
> Looks like we have a ton of problems because devices
> are initialized in a random order, while we
> really want e.g. iommu to be initialized
> earlier than devices.
> 
> This will be helpful for other things, e.g.
> real hardware often is initialized in a specific order,
> creating built-in devices for the board often
> has to happen in a specific order, etc.

In the specific case of PCI bus_master_as there is a simple workaround
by placing a dummy container (which lets us build the AddressSpace) and
then adding the alias region at machine_done time.

This is exactly how MemoryListener is supposed to work, so I would start
from there.

Paolo