Re: [PATCH v2 02/22] PCI: Add API to track PCI devices preserved across Live Update

[Samiullah Khawaja]

On Mon, Feb 23, 2026 at 03:08:19PM -0800, David Matlack wrote:
> On Mon, Feb 23, 2026 at 2:04 PM Samiullah Khawaja <skhawaja@xxxxxxxxxx> wrote:
> > On Thu, Jan 29, 2026 at 09:24:49PM +0000, David Matlack wrote:
>
> > >Drivers can notify the PCI subsystem whenever a device is preserved and
> > >unpreserved with the following APIs:
> > >
> > >  pci_liveupdate_outgoing_preserve(pci_dev)
> > >  pci_liveupdate_outgoing_unpreserve(pci_dev)
> >
> > nit: Preserve and Unpreserve can only be done from outgoing kernel, maybe
> > remove the "outgoing" from the function name.
>
> That's reasonable, I can make that change in v3.

I should have added it earlier, but the same applies to the
pci_liveupdate_incoming_finish() as it can only be done with incoming
kernel. Maybe we can remove incoming from it also for consistency?
> > >+static int pci_flb_preserve(struct liveupdate_flb_op_args *args)
> > >+{
> > >+      struct pci_dev *dev = NULL;
> > >+      int max_nr_devices = 0;
> > >+      struct pci_ser *ser;
> > >+      unsigned long size;
> > >+
> > >+      for_each_pci_dev(dev)
> > >+              max_nr_devices++;
> >
> > This will not work for SRIOV as new devices will be registered when
> > sriov is enabled and the max will increase. As we are not handling VFs
> > with this patch series, this can be fine?
>
> That's right. Since this series does not support VFs
> (pci_liveupdate_outgoing_preserve(VF) will return -EINVAL), I dropped
> the logic from v1 that included the maximum possible number of VFs in
> max_nr_devices.
>
> Once we add support for preserving VFs, we can update this logic.
>
> Another way that pci_liveupdate_outgoing_preserve() could fail due to
> running out of room is if hot-plugged devices are preserved. But I
> don't think that's an important problem to solve right now.