ACK: [SRU][N/O/U][PATCH 0/1] Disable PCI_DYNAMIC_OF_NODES

[Kevin Becker]

On Thu, Aug 1, 2024 at 10:55 AM Roxana Nicolescu
<roxana.nicolescu at canonical.com> wrote:
>
> BugLink: https://bugs.launchpad.net/bugs/2074376
>
> 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 at 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 at 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 at 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.
>
> Roxana Nicolescu (1):
>   UBUNTU: [Config] Disable PCI_DYNAMIC_OF_NODES
>
>  debian.master/config/annotations | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> --

Acked-by: Kevin Becker <kevin.becker at canonical.com>