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

David Matlack
2026-02-02T18:15:26Z

On Sat, Jan 31, 2026 at 10:38 PM Zhu Yanjun <yanjun.zhu@linux.dev> wrote:
>
> 在 2026/1/29 13:24, David Matlack 写道:
> > Add an API to enable the PCI subsystem to track all devices that are
> > preserved across a Live Update, including both incoming devices (passed
> > from the previous kernel) and outgoing devices (passed to the next
> > kernel).
> >
> > Use PCI segment number and BDF to keep track of devices across Live
> > Update. This means the kernel must keep both identifiers constant across
> > a Live Update for any preserved device. VFs are not supported for now,
> > since that requires preserving SR-IOV state on the device to ensure the
> > same number of VFs appear after kexec and with the same BDFs.
> >
> > Drivers that preserve devices across Live Update can now register their
> > struct liveupdate_file_handler with the PCI subsystem so that the PCI
> > subsystem can allocate and manage File-Lifecycle-Bound (FLB) global data
> > to track the list of incoming and outgoing preserved devices.
> >
> > pci_liveupdate_register_fh(driver_fh)
> > pci_liveupdate_unregister_fh(driver_fh)
>
> Can the above 2 functions support the virtual devices? For example,
> bonding, veth, iSWAP and RXE.
>
> These virtual devices do not have BDF. As such, I am not sure if your
> patches take these virtual devices in to account.

No this patch series only supports PCI devices, since those are the
only devices so far we've needed to support.

I am not familiar with any of the devices that you mentioned. If they
are virtual then does that mean it's all just software? In that case I
would be curious to know what problem is solved by preserving them in
the kernel, vs. tearing them down and rebuilding them across a Live
Udpate.