Re: [Qemu-devel] [SeaBIOS] [PATCH 4/6] Mapping of BARs and Bridge regions

[Gerd Hoffmann]

On 03/01/12 23:01, Alexey Korolev wrote:
> On 01/03/12 22:22, Gerd Hoffmann wrote:
>> On 03/01/12 07:57, Alexey Korolev wrote:
>>> In pci_bios_map_regions() we try to reserve memory for 
>>> all entries of root bus regions.
>>> If pci_bios_init_root_regions() fails - e.g no enough space, we create two 
>>> new pci_regions:
>>> r64pref, r64mem and migrate all entries which are 64bit capable to them. 
>>> Migration process
>>> is very simple: delete the entry from one list add to another.
>> It isn't that simple.  There are a bunch of constrains.  First the
>> bridge must be 64bit capable.  All bridges up to the root bus in case of
>> nested bridges.  Second all other prefmem bars of devices behind the
>> bridge must be 64bit capable too.  Again, in case of nested bridges this
>> applies to all devices behind the toplevel bridge.
> It must be simple as we derive 64bit flag from devices behind the bridge at 
> the stage of building topology.
> 
> In other words if the entry at the stage of mapping has 64bit flag it means 
> that the entry and all
> the entries behind it are 64bit capable.
> 
> +    for (i = (MaxPCIBus + 1) * PCI_REGION_TYPE_COUNT ; i < 0; i--) {
> +      .................
> +        is64bit = this_entry->is64bit;
> +        size = 0;
> +        foreach_region_entry(&regions[i-1], entry) {
> +            size += entry->size;
> +            is64bit &= entry->is64bit;
> +        }
>        .................
> +        this_entry->is64bit = is64bit;

This pass looks at the children and clears the is64bit in the parent in
case one of the children isn't 64bit capable.

I think you need a second pass here, clearing the is64bit in all
children in case the parent has is64bit cleared.

cheers,
  Gerd