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Re: [Qemu-devel] [PATCH v1] spapr/pci: Fix primary bus number for PCI br
From: |
David Hildenbrand |
Subject: |
Re: [Qemu-devel] [PATCH v1] spapr/pci: Fix primary bus number for PCI bridges |
Date: |
Fri, 25 Jan 2019 10:28:24 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.1 |
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 <address@hidden>
>
>
> Reviewed-by: Alexey Kardashevskiy <address@hidden>
>
>
Thanks!
--
Thanks,
David / dhildenb