Re: [libvirt] [PATCH v3.5 14/18] qemu: only force an available legacy-PCI slot on domains with pci-root

On Thu, 2016-09-29 at 10:14 -0400, Laine Stump wrote: > Andrea had the right idea when he disabled the "reserve an extra > unused slot" bit for aarch64/virt. For *any* PCI Express-based > machine, it is pointless since 1) an extra legacy-PCI slot can't be > used for hotplug, since hotplug into legacy PCI slots doesn't work on > PCI Express machinetypes, and 2) even for "coldplug" expansion, > everybody will want to expand using Express controllers, not legacy > PCI. > > This patch eliminates the extra slot reserve unless the system has a > pci-root (i.e. legacy PCI) [...] > @@ -1704,23 +1702,35 @@ qemuDomainAssignPCIAddresses(virDomainDefPtr def, > addrs) < 0) > goto cleanup; > > - for (i = 0; i < addrs->nbuses; i++) { > - if (!qemuDomainPCIBusFullyReserved(&addrs->buses[i])) > - buses_reserved = false; > - } > - > - /* Reserve 1 extra slot for a (potential) bridge only if buses > - * are not fully reserved yet. > + /* For domains that have pci-root, reserve 1 extra slot for a > + * (potential) bridge (for future expansion) only if buses are > + * not fully reserved yet (if all buses are fully reserved > + * with manually/previously assigned addresses, any attempt to > + * reserve an extra slot would fail anyway. But if all buses > + * are *not* fully reserved, this extra reservation might push > + * the config to add a new pci-bridge to plug into the final > + * available slot, thus preserving the ability to expand) > * > - * We don't reserve the extra slot for aarch64 mach-virt guests > - * either because we want to be able to have pure virtio-mmio > - * guests, and reserving this slot would force us to add at least > - * a dmi-to-pci-bridge to an otherwise PCI-free topology > + * We only do this for those domains that have pci-root, since > + * those with pcie-root will usually want to expand using PCIe > + * controllers, which we will do after assigning addresses for > + * all *actual* devices. > */ > - if (!buses_reserved && > - !qemuDomainMachineIsVirt(def) && > - qemuDomainPCIAddressReserveNextSlot(addrs, &info) < 0) > - goto cleanup; > + > + if (qemuDomainMachineHasPCIRoot(def)) { Since now you're using info exclusively inside this block, you can move its declaration here as well.