Re: [libvirt] [PATCH v3 15/18] qemu: auto-add pcie-root-port/dmi-to-pci-bridge controllers as needed

On 10/10/2016 02:14 PM, Andrea Bolognani wrote: What can you plug a pci-bridge into on a pseries machine? For all machinetypes, if there is an unaddressed pci-bridge in the config and there is a slot available that accepts a pci-bridge (i.e. pci-root, pci-bridge, or dmi-to-pci-bridge) then we won't be calling virDomainPCIAddressSetGrow() in the first place (since it's only called if no empty slot with correct flags can be found). And I don't know about pseries, but for 440fx, if there isn't a matching empty slot that accepts a pci-bridge at that point, then it's not possible to add one (you already have the one and only pci-root, and you're already trying to add a pci-bridge --> if you have to add a pci-bridge in order to add a pci-bridge, then you're in an infinite recursion). So a dmi-to-pci-bridge is the only thing that could possibly help, and in the cases where there is no pcie-root, it would just mean that you would get an error later when you're told there's no place to plug in the dmi-to-pci-bridge. So it makes sense for me to add a check here to see if the model of addrs->buses[0] is PCIE_ROOT, and only try adding the dmi-to-pci-bridge in that case.