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

[Alexey Korolev <alexey.korolev@endace.com>]

On 02/03/12 20:21, Gerd Hoffmann wrote:
> 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.
It is unnecessary since the parent is not 64bit capable - both the parent and its children would never be mapped to 64bit range.
One thing is missing in my code is reading bridge capabilities - so I've added it.
> cheers,
>   Gerd
>