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

[Paolo Bonzini]

On 09/03/2017 13:11, Marcel Apfelbaum wrote:
> On 03/09/2017 01:13 PM, Paolo Bonzini wrote:
>>
>>
>> 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 <address@hidden>
>>> ---
>>>
>>> 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.
>>
> 
> Hi Paolo,
> 
> This will certainly solve virtio-pci ordering issue, but I am not sure
> it solves the vfio-pci problem. Here is a link to Alex's explanation:
> 
> http://www.mail-archive.com/address@hidden/msg432365.html

Right, VFIO is more complicated (hence "in the specific case of PCI
bus_master_as").  I answered in that thread.

Paolo