Second thing: Booting with an unpatched seabios has bad effects:
[root@localhost ~]# cat /proc/iomem 00000000-000fffff : PCI Bus 0000:10 00000000-00000fff : reserved 00001000-0009fbff : System RAM 0009fc00-0009ffff : reserved 000c0000-000c91ff : Video ROM 000c9800-000ca1ff : Adapter ROM 000ca800-000ccbff : Adapter ROM 000f0000-000fffff : reserved 000f0000-000fffff : System ROM 00100000-3ffdffff : System RAM 01000000-0174bde4 : Kernel code 0174bde5-01d30cff : Kernel data 01eaa000-0202afff : Kernel bss 3ffe0000-3fffffff : reserved fd000000-fdffffff : 0000:00:02.0 fd000000-fdffffff : bochs-drm febc0000-febdffff : 0000:00:03.0 febc0000-febdffff : e1000 febf0000-febf0fff : 0000:00:02.0 febf0000-febf0fff : bochs-drm fec00000-fec003ff : IOAPIC 0 fed00000-fed003ff : HPET 0 fed00000-fed003ff : PNP0103:00 fee00000-fee00fff : Local APIC feffc000-feffffff : reserved fffc0000-ffffffff : reserved
"PCI Bus 0000:10" is bogus and "PCI Bus 0000:00" isn't there at all.
Yes, you shouldn't use pxb if you are not using the corresponding SeaBIOS. However, as I understand we always attach a SeaBIOS binary with a QEMU release, so we should be OK with this.
IMO the qemu side should be more robust and not assume specific guest behavior. The guest firmware simply not configuring the pxb shouldn't cause the resources for bus 0 breaking that badly. pxb not working if you run firmware without pxb support is ok. But everything else should continue to work as it did before.