Re: [PATCH v3 02/24] PCI: Add API to track PCI devices preserved across Live Update

[David Matlack]

On Thu, Apr 2, 2026 at 2:29 PM Yanjun.Zhu <yanjun.zhu@xxxxxxxxx> wrote:
> On 3/23/26 4:57 PM, David Matlack wrote:

> > +config PCI_LIVEUPDATE
> > +     bool "PCI Live Update Support (EXPERIMENTAL)"
> > +     depends on PCI && LIVEUPDATE
> > +     help
> > +       Support for preserving PCI devices across a Live Update. This option
> > +       should only be enabled by developers working on implementing this
> > +       support. Once enough support as landed in the kernel, this option
> > +       will no longer be marked EXPERIMENTAL.
> > +
> > +       If unsure, say N.
>
> Currently, it only supports 'n' or 'y'. Is it possible to add 'm'
> (modular support)?
>
> This would allow the feature to be built as a kernel module. For
> development
>
> purposes, modularization means we only need to recompile a single module
>
> for testing, rather than rebuilding the entire kernel. Compiling a
> module should
>
> be significantly faster than a full kernel build.

I don't think it is possible for CONFIG_PCI_LIVEUPDATE to support 'm'.
pci_setup_device() (which is under CONFIG_PCI) needs to call
pci_liveupdate_setup_device(), and CONFIG_PCI cannot be built as a
module. This call is necessary so the PCI core knows whether a device
being enumerated was preserved across a previous Live Update.