linux-kernel - Re: [PATCH] PCI: Fix crash during pci_dev hot-unplug on pseries KVM guest

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Message-ID: <CAL_Jsq+Mojbw9AXPZmGbzDbW7Tj=6zhBWtSKKdqrVhR=AUnp_g@mail.gmail.com>
Date: Thu, 11 Jul 2024 13:34:19 -0600
From: Rob Herring <robh@...nel.org>
To: Amit Machhiwal <amachhiw@...ux.ibm.com>, kernel-team@...ts.ubuntu.com
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linuxppc-dev@...ts.ozlabs.org, kvm-ppc@...r.kernel.org, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Lizhi Hou <lizhi.hou@....com>, 
	Vaibhav Jain <vaibhav@...ux.ibm.com>, Nicholas Piggin <npiggin@...il.com>, 
	Michael Ellerman <mpe@...erman.id.au>, Vaidyanathan Srinivasan <svaidy@...ux.ibm.com>, 
	Kowshik Jois B S <kowsjois@...ux.ibm.com>
Subject: Re: [PATCH] PCI: Fix crash during pci_dev hot-unplug on pseries KVM guest

+Ubuntu kernel team

On Thu, Jul 11, 2024 at 8:21 AM Amit Machhiwal <amachhiw@...ux.ibm.com> wrote:
>
> Hi Rob,
>
> On 2024/07/11 06:20 AM, Rob Herring wrote:
> > On Wed, Jul 3, 2024 at 8:17 AM Amit Machhiwal <amachhiw@...ux.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@...ntu:~# 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)

Rob