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Re: [Qemu-ppc] [PATCH] spapr/pci: populate PCI DT in reverse order
From: |
Nikunj A Dadhania |
Subject: |
Re: [Qemu-ppc] [PATCH] spapr/pci: populate PCI DT in reverse order |
Date: |
Wed, 23 Dec 2015 11:17:16 +0530 |
User-agent: |
Notmuch/0.20.2 (http://notmuchmail.org) Emacs/24.5.1 (x86_64-redhat-linux-gnu) |
David Gibson <address@hidden> writes:
> On Thu, Dec 17, 2015 at 09:43:29AM +0100, Greg Kurz wrote:
>> On Thu, 3 Dec 2015 15:53:17 +0100
>> Greg Kurz <address@hidden> wrote:
>>
>> > On Tue, 1 Dec 2015 22:48:38 +0100
>> > Thomas Huth <address@hidden> wrote:
>> >
>> > > On 30/11/15 11:45, Greg Kurz wrote:
>> > > > Since commit 1d2d974244c6 "spapr_pci: enumerate and add PCI device
>> > > > tree", QEMU
>> > > > populates the PCI device tree in the opposite order compared to SLOF.
>> > > >
>> > > > Before 1d2d974244c6:
>> > > >
>> > > > Populating /address@hidden
>> > > > 00 0000 (D) : 1af4 1000 virtio [ net ]
>> > > > 00 0800 (D) : 1af4 1001 virtio [ block ]
>> > > > 00 1000 (D) : 1af4 1009 virtio [ network ]
>> > > > Populating /address@hidden/address@hidden
>> > > >
>> > > >
>> > > > 7e5294b8 : /address@hidden
>> > > > 7e52b998 : |-- address@hidden
>> > > > 7e52c0c8 : |-- address@hidden
>> > > > 7e52c7e8 : +-- address@hidden ok
>> > > >
>> > > > Since 1d2d974244c6:
>> > > >
>> > > > Populating /address@hidden
>> > > > 00 1000 (D) : 1af4 1009 virtio [ network ]
>> > > > Populating /address@hidden/address@hidden
>> > > > 00 0800 (D) : 1af4 1001 virtio [ block ]
>> > > > 00 0000 (D) : 1af4 1000 virtio [ net ]
>> > > >
>> > > >
>> > > > 7e5e8118 : /address@hidden
>> > > > 7e5ea6a0 : |-- address@hidden
>> > > > 7e5eadb8 : |-- address@hidden
>> > > > 7e5eb4d8 : +-- address@hidden ok
>> > > >
>> > > > This behaviour change is not actually a bug since no assumptions
>> > > > should be
>> > > > made on DT ordering. But it has no real justification either, other
>> > > > than
>> > > > being the consequence of the way fdt_add_subnode() inserts new elements
>> > > > to the front of the FDT rather than adding them to the tail.
>> > > >
>> > > > This patch reverts to the historical SLOF ordering by walking PCI
>> > > > devices in
>> > > > reverse order.
>> > >
>> > > I've applied your patch here locally, and indeed, the device tree looks
>> > > nicer to me, too, when the nodes are listed in ascending order.
>> > >
>> > > Tested-by: Thomas Huth <address@hidden>
>> > >
>> > >
>> >
>>
>> Ping ?
>
> Sorry I didn't reply.
>
> I'm still dubious about this. It seems like a fair bit of effort to
> restore a behaviour that the client isn't supposed to be relying on
> anyway.
>
> Plus, the version with the changed order is already released, so
> applying this will mean a second behaviour change.
The behaviour change was not intentional by me, so I would vote for
restoring the old order.
Reviewed-by: Nikunj A Dadhania <address@hidden>
Regards
Nikunj