Re: [Qemu-devel] [PATCH] pci: add standard bridge device

[Wen Congyang]

At 11/01/2011 04:44 PM, Michael S. Tsirkin Write:
> On Tue, Nov 01, 2011 at 09:27:25AM +0800, Wen Congyang wrote:
>> Hi, Michael S. Tsirkin
>>
>> At 09/26/2011 03:08 PM, Michael S. Tsirkin Write:
>>> On Mon, Sep 26, 2011 at 02:18:15PM +0800, Wen Congyang wrote:
>>>> Hi, Michael S. Tsirkin 
>>>>
>>>> At 07/04/2011 05:43 PM, Michael S. Tsirkin Write:
>>>>> This adds support for a standard pci to pci bridge,
>>>>> enabling support for more than 32 PCI devices in the system.
>>>>> To use, specify the device id as a 'bus' option.
>>>>> Example:
>>>>>   -device pci-bridge,id=bridge1 \
>>>>>   -netdev user,id=u \
>>>>>   -device ne2k_pci,id=net2,bus=bridge1,netdev=u
>>>>>
>>>>> TODO: device hotplug support.
>>>>
>>>> Do you have any plan to implement this?
>>>
>>> I think this will be needed before merging the bridge code.
>>
>> What will you plan to support?
>>
>> 1. all PCI-to-PCI bridge is not hotpluggable.
>>                host bridge
>>                    |
>>          ---------------------
>>           |                 |
>>         bridge            bridge       <= *not* hotpluggable
>>           |                 |
>>      -----------       ------------
>>       |       |         |        |
>>     slot     slot      slot     slot   <= hotplug here 
>>
>>
>> 2. PCI-to-PCI bridge is hotpluggable.
>>              bridge
>>                |
>>       -------------------
>>          |           |
>> bridge on slot   bridge on slot         <= hot-plug here
>>          |           |
>>       -------     -------
>>        |   |       |   |
>>      slot slot   slot slot        <= hot-plug here 
>>
>>>
>>>> I read the qemu's code, and find that qemu uses PIIX4_PM to support
>>>> pci device hot plugging on PCI bus 0. How to support it on the other
>>>> bus? Add PIIX4_PM to each PCI bus or implement a new power management?
>>>>
>>>> Thanks
>>>> Wen Congyang
>>>
>>> There are many valid options. One is shpc interface.
>>> I started looking into this but got preempted by other
>>> tasks. Hope to get back to this at some point.
>>
>> Some old OS does not support shpc. So I think it's better to use ACPI to do 
>> it.
>>
>> Currently, we get which device is removed or inserted by reading the I/O port
>> 0xae00(length: 8 bytes), and _EJ0 method uses I/O port 0xae08(length: 4 
>> bytes).
>> How do we determine this I/O address? Is there any spec to describe it?
>>
>> Thanks
>> Wen Congyang
> 
> Can we discuss these questions on the mailing list?

No problem.
I have cced qemu mailing list.

Thanks
Wen Congyang