[SeaBIOS] hotplug failure issue on pci-bridge

[Liu, Jing2]

Hi,

Recently, we tried some hotplug issues. The case is: when hotplug a 
device (e.g. iGPU) onto pci-bridge after guest booting up, guest reports 
"BAR 2: no space for [mem size 0x40000000 64bit pref]" etc.

Seabios checks all the devices under the pci-bridge when qemu launching 
the guest, and only allocates "size=ALIGN(sum, align)" of memory space 
for pci-bridge mem and pref-mem windows. So if we hotplug a big pci 
device like Intel GPU which needs 256M mem/pref-mem or bigger, it will 
fail.

If my understanding is right, we may need some other logic of the memory 
allocation in seabios?

Looking forward to the advice.

Thanks,
Jing