Re: [Qemu-devel] [PATCH v1] spapr/pci: Fix primary bus number for PCI bridges

[David Hildenbrand <david@redhat.com>]

On 24.01.19 03:48, Alexey Kardashevskiy wrote:
> 
> 
> On 23/01/2019 19:24, David Hildenbrand wrote:
>> While looking at the s390x implementation, looks like spapr has a
>> similar BUG when building the topology.
>>
>> The primary bus number corresponds always to the bus number of the
>> bus the bridge is attached to.
>>
>> Right now, if we have two bridges attached to the same bus (e.g. root
>> bus) this is however not the case. The first bridge will have primary
>> bus 0, the second bridge primary bus 1, which is wrong. Fix the assignment.
>>
>> While at it, drop setting the PCI_SUBORDINATE_BUS temporarily to 0xff.
>> Setting it temporarily to that value (as discussed e.g. in [1]), is
>> only relevant for a running system that probes the buses. The value is
>> effectively unused for us just doing a DFS.
> 
> What is DFS?

Depth-first search :)

> 
>>
>> [1] http://www.science.unitn.it/~fiorella/guidelinux/tlk/node76.html
>>
>> Note: Is hotplug of bridges supported? I can't find where the topology
>> is fixed up when hotplugging a PCI bridge. (e.g. bus numbers assigned
>> and PCI_SUBORDINATE_BUS of path to the root updated). But maybe we are
>> excluding bridges or this is not necessary for some reason.
>>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
> 
> 
> Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> 
> 

Thanks!


-- 

Thanks,

David / dhildenb