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

From: David Hildenbrand
Subject: Re: [Qemu-ppc] [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>




David / dhildenb

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