On Sun, 2015-06-14 at 17:59 -0400, Kevin O'Connor wrote: > There are x86 systems with multiple separate PCI root buses where one > can access the pci config space of all the buses using the same 0x0cf8 > IO space. During system setup, the multiple PCI root buses are each > configured to only respond to PCI config accesses within its range of > bus numbers. So if "root1" is configured for bus ids between 64-128, > then it will only forward the request if the bus id in the request is > between 64-128. > > I suspect in your PPC example that the separate root buses all had > separate io/memory space as well and thus were completely separate. > (That is, they don't share the equivalent of IO 0x0cf8.) If so, > that's different from how the x86 qemu code and the x86 systems I was > discussing above work.
Correct, my point is that qemu shouldn't be made to rely on the stable bus numbers. Why not use the mmconfig address instead ? That way you can factor the bus number in via an offset if it's relevant or provide a completely different address if the busses are separate. Ben.
