Re: [PATCH v8 02/12] PCI: liveupdate: Track outgoing preserved PCI devices

[David Matlack]

On Tue, Sep 15, 2026 at 8:10 PM Zhu Yanjun <yanjun.zhu@xxxxxxxxx> wrote:
>
> 在 2026/7/28 15:09, David Matlack 写道:
> > Add APIs to allow drivers to notify the PCI core of which devices are
> > being preserved across a Live Update for the next kernel, i.e.
> > "outgoing" devices.
> >
> > Drivers must notify the PCI core when devices are preserved so that the
> > PCI core can update its FLB data (struct pci_ser) and track the list of
> > outgoing devices. pci_liveupdate_preserve() notifies the PCI core that a
> > device must be preserved across Live Update. pci_liveupdate_unpreserve()
> > reverses this (cancels the preservation of the device).
>
> Hi David,
>
> I have a question about the pci_liveupdate_preserve() and
> pci_liveupdate_unpreserve() APIs.
>
> Is it supported to call these APIs multiple times for the same PCI
> device? For example, a driver could do:
>
> pci_liveupdate_preserve(pdev) -- > pci_liveupdate_unpreserve(pdev) -- >
> perform some operations -- > pci_liveupdate_preserve(pdev) again, before
> the actual Live Update starts.
>
>  From the implementation, it looks like an unpreserved pci_dev_ser entry
> can be reused, so I wanted to confirm whether this preserve -- >
> unpreserve -- > preserve sequence is an intended and supported usage.

Yes that is a completely supported use-case. A device can be preserved
and unpreserved any number of times up until pci_device_shutdown(),
where the preservation status of the device is frozen (see patch 10).