On 2/2/26 10:14 AM, David Matlack wrote:

On Sat, Jan 31, 2026 at 10:38 PM Zhu Yanjun [off-list ref] wrote:

quoted

在 2026/1/29 13:24, David Matlack 写道:

quoted

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.

Bonding, veth, rxe, and siw can be used in KVM environments.

Although these are software-only virtual devices with no associated 
hardware,

they may maintain state that is observable by userspace.

As a result, Live Update should preserve their state across the update.

Zhu Yanjun