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: <4998497c-87e8-4849-8442-b7281c627884@linux.dev>
Date: Mon, 1 Dec 2025 09:16:06 -0800
From: Zhu Yanjun <yanjun.zhu@...ux.dev>
To: David Matlack <dmatlack@...gle.com>
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


在 2025/12/1 9:10, David Matlack 写道:
> 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?


IIRC, I used FC 42 default config. Perhaps you can make tests with it. 
If this problem can not be reproduced, I will share my config with you.

Yanjun.Zhu


-- 
Best Regards,
Yanjun.Zhu