linux-kernel - Re: [PATCH 00/21] vfio/pci: Base support to preserve a VFIO device file across Live Update

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Message-ID: <CALzav=eigAYdw5-hzk1MAHWBU29yJK4_WWTd0dyoBN91bnRoZQ@mail.gmail.com>
Date: Mon, 1 Dec 2025 09:10:14 -0800
From: David Matlack <dmatlack@...gle.com>
To: Zhu Yanjun <yanjun.zhu@...ux.dev>
Cc: Alex Williamson <alex@...zbot.org>, Adithya Jayachandran <ajayachandra@...dia.com>, 
	Alex Mastro <amastro@...com>, Alistair Popple <apopple@...dia.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Chris Li <chrisl@...nel.org>, David Rientjes <rientjes@...gle.com>, 
	Jacob Pan <jacob.pan@...ux.microsoft.com>, Jason Gunthorpe <jgg@...dia.com>, 
	Jason Gunthorpe <jgg@...pe.ca>, Josh Hilke <jrhilke@...gle.com>, Kevin Tian <kevin.tian@...el.com>, 
	kvm@...r.kernel.org, Leon Romanovsky <leonro@...dia.com>, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, linux-pci@...r.kernel.org, 
	Lukas Wunner <lukas@...ner.de>, Mike Rapoport <rppt@...nel.org>, Parav Pandit <parav@...dia.com>, 
	Pasha Tatashin <pasha.tatashin@...een.com>, Philipp Stanner <pstanner@...hat.com>, 
	Pratyush Yadav <pratyush@...nel.org>, Saeed Mahameed <saeedm@...dia.com>, 
	Samiullah Khawaja <skhawaja@...gle.com>, Shuah Khan <shuah@...nel.org>, 
	Tomita Moeko <tomitamoeko@...il.com>, Vipin Sharma <vipinsh@...gle.com>, William Tu <witu@...dia.com>, 
	Yi Liu <yi.l.liu@...el.com>, Yunxiang Li <Yunxiang.Li@....com>
Subject: Re: [PATCH 00/21] vfio/pci: Base support to preserve a VFIO device
 file across Live Update

On Mon, Dec 1, 2025 at 7:49 AM Zhu Yanjun <yanjun.zhu@...ux.dev> wrote:
> 在 2025/11/27 20:56, Zhu Yanjun 写道:
> > Hi, David
> >
> > ERROR: modpost: "liveupdate_register_file_handler" [drivers/vfio/pci/
> > vfio-pci-core.ko] undefined!
> >
> > ERROR: modpost: "vfio_pci_ops" [drivers/vfio/pci/vfio-pci-core.ko]
> > undefined!
> > ERROR: modpost: "liveupdate_enabled" [drivers/vfio/pci/vfio-pci-core.ko]
> > undefined!
> > ERROR: modpost: "liveupdate_unregister_file_handler" [drivers/vfio/pci/
> > vfio-pci-core.ko] undefined!
> > ERROR: modpost: "vfio_device_fops" [drivers/vfio/pci/vfio-pci-core.ko]
> > undefined!
> > ERROR: modpost: "vfio_pci_is_intel_display" [drivers/vfio/pci/vfio-pci-
> > core.ko] undefined!
> > ERROR: modpost: "vfio_pci_liveupdate_init" [drivers/vfio/pci/vfio-
> > pci.ko] undefined!
> > ERROR: modpost: "vfio_pci_liveupdate_cleanup" [drivers/vfio/pci/vfio-
> > pci.ko] undefined!
> > make[4]: *** [scripts/Makefile.modpost:147: Module.symvers] Error 1
> > make[3]: *** [Makefile:1960: modpost] Error 2
> >
> > After I git clone the source code from the link https://github.com/
> > dmatlack/linux/tree/liveupdate/vfio/cdev/v1,
> >
> > I found the above errors when I built the source code.
> >
> > Perhaps the above errors can be solved by EXPORT_SYMBOL.
> >
> > But I am not sure if a better solution can solve the above problems or not.
>
> I reviewed this patch series in detail. If I’m understanding it
> correctly, there appears to be a cyclic dependency issue. Specifically,
> some functions in kernel module A depend on kernel module B, while at
> the same time certain functions in module B depend on module A.
>
> I’m not entirely sure whether this constitutes a real problem or if it’s
> intentional design.

Thanks for your report. Can you share the .config file you used to
generate these errors?