Re: [Qemu-devel] [PATCH v3 5/5] docs: update documentation considering PCIE-PCI bridge

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Aug 02, 2017 at 06:36:29PM +0300, Marcel Apfelbaum wrote:
> > > > > > Can dmi-pci support shpc? why doesn't it? For compatibility?
> > > > > 
> > > > > I don't know why, but the fact that it doesn't is the reason libvirt
> > > > > settled on auto-creating a dmi-pci bridge and a pci-pci bridge under
> > > > > that for Q35. The reasoning was (IIRC Laine's words correctly) that the
> > > > > dmi-pci bridge cannot receive hotplugged devices, while the pci-pci
> > > > > bridge cannot be connected to the root complex. So both were needed.
> > > > > 
> > > > > Thanks
> > > > > Laszlo
> > > > 
> > > > OK. Is it true that dmi-pci + pci-pci under it will allow hotplug
> > > > on Q35 if we just flip the bit in _OSC?
> > > 
> > > Marcel, what say you?... :)
> 
> Good news, works with:
>    -device i82801b11-bridge,id=b1
>    -device pci-bridge,id=b2,bus=b1,chassis_nr=1,msi=off

And presumably it works for modern windows?
OK, so it looks like patch 1 is merely a bugfix, I'll merge it for 2.10.

> Notice bridge's msi=off until the following kernel bug will be merged:
>   https://www.spinics.net/lists/linux-pci/msg63052.html

Does libvirt support msi=off as a work-around?

> 
> Thanks,
> Marcel

-- 
MST