[Bug 2074376] Re: Disable PCI_DYNAMIC_OF_NODES in Ubuntu

This bug is awaiting verification that the linux-
hwe-6.11/6.11.0-9.9~24.04.1 kernel in -proposed solves the problem.
Please test the kernel and update this bug with the results. If the
problem is solved, change the tag 'verification-needed-noble-linux-
hwe-6.11' to 'verification-done-noble-linux-hwe-6.11'. If the problem
still exists, change the tag 'verification-needed-noble-linux-hwe-6.11'
to 'verification-failed-noble-linux-hwe-6.11'.


If verification is not done by 5 working days from today, this fix will
be dropped from the source code, and this bug will be closed.


See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how
to enable and use -proposed. Thank you!


** Tags added: kernel-spammed-noble-linux-hwe-6.11-v2 verification-needed-noble-linux-hwe-6.11

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https://bugs.launchpad.net/bugs/2074376

Title:
Disable PCI_DYNAMIC_OF_NODES in Ubuntu

Status in The Ubuntu-power-systems project:
Fix Released
Status in linux package in Ubuntu:
Fix Released
Status in linux source package in Noble:
Fix Released
Status in linux source package in Oracular:
Fix Released

Bug description:
This came in via KTML from upstream. It is part of a discussion
between upstream and IBM reporting a bug which occurs in KVM:

Rob Herring <robh@kernel.org> writes:

>> On 2024/07/11 06:20 AM, Rob Herring wrote:
>>> On Wed, Jul 3, 2024 at 8:17 AM Amit Machhiwal <amachhiw@linux.ibm.com> wrote:
>>>>
>>>> With CONFIG_PCI_DYNAMIC_OF_NODES [1], a hot-plug and hot-unplug sequence
>>>> of a PCI device attached to a PCI-bridge causes following kernel Oops on
>>>> a pseries KVM guest:
>>>
>>> Can I ask why you have this option on in the first place? Do you have
>>> a use for it or it's just a case of distros turn on every kconfig
>>> option.
>>
>> Yes, this option is turned on in Ubuntu's distro kernel config where the issue
>> was originally reported, while Fedora is keeping this turned off.
>>
>> root@ubuntu:~# cat /boot/config-6.8.0-38-generic | grep PCI_DYN
>> CONFIG_PCI_DYNAMIC_OF_NODES=y
>
> Ubuntu should turn off this option. For starters, it is not complete
> to be usable. Eventually, it should get removed in favor of some TBD
> runtime option.
>
> (And we should fix the crash too)

This option is described in the config system as:

This option enables support for generating device tree nodes for some
PCI devices. Thus, the driver of this kind can load and overlay
flattened device tree for its downstream devices.
.
Once this option is selected, the device tree nodes will be generated
for all PCI bridges.

Open Firmware (OF) would be used for KVM for UEFI mode. The reported
bug was related to hot-unplugging PCI devices. My guess would be that
this probably is not of much use to the majority of users and might
even go away. So it should really be disabled in Ubuntu, too.

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