+As opposed to PCI-2-PCI bridge's secondary bus, PXB's bus
+is a primary bus and can be associated with a NUMA node
+(different from the main host bridge) allowing the guest OS
+to recognize the proximity of a pass-through device to
+other resources as RAM and CPUs.
+A detailed command line would be:
+[qemu-bin + storage options]
+-bios [seabios-dir]/out/bios.bin -L [seabios-dir]/out/
+-device pxb-device,id=bridge1,bus=pci.0,numa_node=1,bus_nr=4 -netdev
+-device pxb-device,id=bridge2,bus=pci.0,numa_node=0,bus_nr=8 -device
+-device pxb-device,id=bridge3,bus=pci.0,bus_nr=40 -drive
+Here you have:
+ - 2 NUMA nodes for the guest, 0 and 1. (both mapped to the same NUMA node in
host, but you can and should put it in different host NUMA nodes)
+ - a pxb host bridge attached to NUMA 1 with an e1000 behind it
+ - a pxb host bridge attached to NUMA 0 with an e1000 behind it
+ - a pxb host bridge not attached to any NUMA with a hard drive behind it.
+The PXB is composed by:
+- HostBridge (TYPE_PXB_HOST)
+ The host bridge allows to register and query the PXB's rPCI root bus in QEMU.
+ It is a regular PCI Device that resides on the piix host-bridge bus and its
bus uses the same PCI domain.
+ However, the bus behind is exposed through ACPI as a primary PCI bus and
starts a new PCI hierarchy.
+ The interrupts from devices behind the PXB are routed through this device
the same as if it were a
+ PCI-2-PCI bridge. The _PRT follows the i440fx model.
+ Created automatically as part of init sequence.
+ When adding a device to PXB it is attached to the bridge for two reasons:
+ - Using the bridge will enable hotplug support
+ - All the devices behind the bridge will use bridge's IO/MEM windows
+ the PCI address space.