Re: [SeaBIOS] [PATCH 2/2] fw/pci: map memory and IO regions for multiple pci root buses

[Marcel Apfelbaum]

On Mon, 2014-11-24 at 13:28 +0100, Gerd Hoffmann wrote:
> On Mo, 2014-11-24 at 11:47 +0200, Marcel Apfelbaum wrote:
> > Removed the assumption that the system has only one primary root bus.
> > When mapping memory and IO regions go over all buses, skipping
> > secondary and absent buses.

Hi Gerd,
Thanks for the review.
> I guess there are qemu patches adding support for multiple pci busses
> somewhere?

Yes, an RFC will be released soon on QEMU mailing list,
is a work in progress and I am currently trying to decide
if I wait for a fully functional series or release is sooner
for comments.
> > for (i = 0; i <= MaxPCIBus; i++) {
> >    struct pci_region *r_io = &bus[i].r[PCI_REGION_TYPE_IO];
> >    u64 sum = pci_region_sum(r_io);
> >    if (bus[i].bus_dev || !sum)
> >        continue;
> >    sum_pci = ALIGN(sum_pci, sum);
> >    sum_free = ALIGN(sum_free, sum);
> >    if (sum + sum_pci < 0x4000) {
> >        /* traditional region is big enough, use it */
> >        r_io->base = 0xc000 + sum_pci;
> >        sum_pci += sum;
> >    } else if (sum < pci_io_low_end - 0x1000 - sum_free) {
> >        /* use the larger region at 0x1000 */
> >        r_io->base = 0x1000 + sum_free;
> >        sum_free += sum;
> >    } else {
> >        /* not enough io address space -> error out */
> >        return -1;
> >    }
>
> Hmm, that assigns the io regions in bus order.  I think it would be
> better to integrate this with the packing logic we already have:
> regions are sorted by size for best packing.  Regions behind pci bridges
> are grouped together.  I think we could group regions belonging to a pci
> bus in a simliar way.

You are right, but only partial. Let me explain (as I understand it).
The devices IO regions behind the bus are *already* packed (sorted by size).
The buses themselves are indeed not sorted by their total IO space.
The same is happening in pci_bios_init_root_regions_mem with the MMIO regions.

It seems that what I have to do is simply replace the current bus enumeration:
    for (i = 0; i <= MaxPCIBus; i++) {
with one that goes over the sorted list of buses in decreasing order of their
total mem/IO consumed.

Do you agree?

Also, it seems cleaner to add a patch on top of this (and re-sending the series again)
since while not optimal, it is still correct.

Thanks,
Marcel
> cheers,
>   Gerd