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Re: [Qemu-devel] [PATCH] pci: add standard bridge device
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH] pci: add standard bridge device |
Date: |
Tue, 1 Nov 2011 13:48:17 +0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, Nov 01, 2011 at 04:49:08PM +0800, Wen Congyang wrote:
> 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
It seems easier to start with a non hotpluggable bridge.
I'm still trying to understand how is bridge hotplug
supposed to work under ACPI, which wants all devices
described in a static page.
> >>>
> >>>> 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.
Yes, but ACPI can drive SHPC.
> >> 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?
I don't think so.
> >> Thanks
> >> Wen Congyang
> >
> > Can we discuss these questions on the mailing list?
>
> No problem.
> I have cced qemu mailing list.
>
> Thanks
> Wen Congyang