[vbox-dev] Bridge Device Enumeration

Ananth Pallapothu apallapothu at gmail.com
Wed Feb 3 02:40:07 UTC 2016

Hello Experts,

I have a pluggable bridge device hooked up to the Virtual Machine (VBox
5.0.10) on Linux host (4.4.7), ICH9 chipset. Problem is that fakeBIOS isn't
able to enumerate devices behind the bridge.

I do see whole bunch of accesses targeted towards the bridge, reading class
code, subordinate bus etc and all responses are appropriate (inline with
PCI bridge spec) but never were there any transactions targeted towards
subordinate bus to identify end point device.

1. Are there any specific restrictions on the "type" of switches that bios
can handle ?
2. Is the BIOS capable of enumerating devices that are behind the bridge
for a pluggable device ?
3. Is the bios hardcoded to ONLY support "ich9pcibridge: 8086-2448"

I looked through the source code pcibios.c (Is this right file to look ? )
and see that there is a code snippet that looks behind the bridge (access
class code, subordinate bus etc), BUT when I attached gdb during the run
and tried to break-in for debug, gdb process never breaked in inside, void
BIOSCALL PCIxx(function)(volatile pci_regs_t r) or uint16_t
PCIxx(find_device)(uint32_t search_item, uint16_t index, int search_class)

Thanks for the suggestions in advance.

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