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

David Matlack
2026-03-02T18:14:58Z

On Sun, Mar 1, 2026 at 11:22 AM Jason Gunthorpe <jgg@nvidia.com> wrote:
>
> On Fri, Feb 27, 2026 at 09:04:49AM -0700, Alex Williamson wrote:
>
> > Not only fabric topology, but also routing.
>
> Yes
>
> > ACS overrides on the
> > command line would need to be enforced between the original and kexec
> > kernel such that IOMMU groups are deterministic. Thanks,
>
> That's a good point, I think as a reasonable starting point we should
> require live update preserved devices to have singleton iommu_groups
> on both sides. That is easy to check and enforce, and it doesn't
> matter how the administrator makes that happen.

I can add that in the next version.

> You also can't change the ACS flags while traffic is flowing because
> that changes the fabric routing too. This should take care to enforce
> that restriction as well.

I'll look into this but will probably defer it to a future series. We
need several more pieces in place until we are ready to support
traffic to/from preserved devices during the Live Update.