Re: [Qemu-devel] [PATCHv2-RFC 0/2] RFC: standard pci bridge device

[Wen Congyang]

At 02/13/2012 05:15 PM, Michael S. Tsirkin Wrote:
> Here's a new version of the patch. It works for me.
> Deep nesting of bridges is supported.
> You need a small BIOS patch to support the OSHP method
> if you want hotplug to work. I will post this separately.
> We'd need a full ACPI driver to make hotplug work for guests
> without an SHPC driver (e.g. windows XP).
> Management support will also be needed.
> 
> One small wrinkle is that the pci_addr property
> wants data in a format bus:device.function which is
> broken as guests can change bus numbers.
> For testing I used the 'addr' property which
> encodes slot*8+function#. We probably want to
> extend pci_addr in some way (e.g. :device.function ?
> Thoughts?).

What about using id+device(slot)+function to set the address?

> 
> The SHPC controller supports up to 31 devices
> (out of 32 slots) so slot 0 doesn't support hotplug.
> Non hot-pluggable devices behind the bridge
> don't work currectly (we'll try to unplug them)
> so don't do this.
> For now I just blocked adding devices in slot 0,
> in the future it might be possible to add
> a non-hotpluggable device there.
> 
> Example:
> 
> qemu-system-x86_64  -enable-kvm -m 1G
>  -drive file=/home/mst/rhel6.qcow2
> -netdev
> tap,id=foo,ifname=msttap0,script=/home/mst/ifup,downscript=no,vhost=on
> -device pci-bridge,id=bog
> -device virtio-net-pci,netdev=foo,bus=bog,addr=8
> 
> 
> Hot-unplug currently causes qemu to crash, this
> happens without this patch too, so I'm not worried :)

How to trigger this bug without this patch?

Thanks
Wen Congyang

> 
> New since v1:
>       hotplug support
>