Re: [PATCH v2 03/22] PCI: Inherit bus numbers from previous kernel during Live Update

[David Matlack <dmatlack@google.com>]

On Tue, Feb 24, 2026 at 1:36 AM Pranjal Shrivastava <praan@google.com> wrote:
> On Thu, Jan 29, 2026 at 09:24:50PM +0000, David Matlack wrote:

> > +     if (pci_liveupdate_incoming_nr_devices())
> > +             return false;
>
> Following the comment on Patch 2 regarding propagating errors, the check
> if (pci_liveupdate_incoming_nr_devices()) should be made explicit to
> distinguish between "Preservation Active" and "Retrieval Failed".

As mentioned in the previous patch, the errors mean "no incoming
devices" rather than "retrieval failed".

> >                               while (parent->parent) {
> > -                                     if ((!pcibios_assign_all_busses()) &&
> > +                                     if (!assign_all_busses &&
> >                                           (parent->busn_res.end > max) &&
> >                                           (parent->busn_res.end <= max+i)) {
> >                                               j = 1;
>
> Looks like we over-ride the pci=assign-busses boot param here.
> We should document how this change affects the pci=assign-busses kernel
> command line. If both are present, the inheritance required by LUO would
> likely take precedence to prevent DMA corruption, but a doc update & a
> warning to the user would be nice.

Good call, I'll add a log message and update kernel-parameters.txt in v3.