Re: [PATCH v5 17/20] vfio: selftests: Add vfio_pci_liveupdate_kexec_test

[Vipin Sharma]

On Sun, Jul 26, 2026 at 05:40:54PM -0700, Zhu Yanjun wrote:
> 
> 在 2026/7/14 8:15, Vipin Sharma 写道:
> > Add a selftest to exercise preserving a vfio-pci device across a Live
> > Update. For now the test is extremely simple and just verifies that the
> > device file can be preserved and retrieved. In the future this test will
> > be extended to verify more parts about device preservation as they are
> > implemented.
> > 
> > This test is added to TEST_GEN_PROGS_EXTENDED since it must be run
> > manually along with a kexec.
> > 
> > To run this test manually:
> > 
> >   $ tools/testing/selftests/vfio/scripts/setup.sh 0000:00:04.0
> >   $ tools/testing/selftests/vfio/vfio_pci_liveupdate_kexec_test --stage 1 0000:00:04.0
> # ls /dev
> autofs           disk       iommu         mem     rtc0      tty10 tty21 
> tty32  tty43  tty54  tty8    ttyS18  ttyS29   uinput  vcs6   vcsu4       
> virtio-ports
> block            dma_heap   kmsg          mqueue  sg0       tty11 tty22 
> tty33  tty44  tty55  tty9    ttyS19  ttyS3    urandom vcsa   vcsu5       
> vport2p1
> bsg              dri        kvm           net     shm       tty12 tty23 
> tty34  tty45  tty56  ttyS0   ttyS2   ttyS30   usbmon0 vcsa1  vcsu6       
> vsock
> btrfs-control    fd         liveupdate    null    snapshot  tty13 tty24 
> tty35  tty46  tty57  ttyS1   ttyS20  ttyS31   usbmon1 vcsa2  vda         
> watchdog
> bus              full       log           nvram   snd       tty14 tty25 
> tty36  tty47  tty58  ttyS10  ttyS21  ttyS4    usbmon2 vcsa3  vda1       
>  watchdog0
> cdrom            fuse       loop-control  port    sr0       tty15 tty26 
> tty37  tty48  tty59  ttyS11  ttyS22  ttyS5    userfaultfd vcsa4  vda2       
>  zero
> char             hidraw0    lp0           ppp     stderr    tty16 tty27 
> tty38  tty49  tty6   ttyS12  ttyS23  ttyS6    vcs vcsa5  vda3         zram0
> console          hpet       lp1           ptmx    stdin     tty17 tty28 
> tty39  tty5   tty60  ttyS13  ttyS24  ttyS7    vcs1  vcsa6  vfio
> core             hugepages  lp2           pts     stdout    tty18 tty29 
> tty4   tty50  tty61  ttyS14  ttyS25  ttyS8    vcs2  vcsu   vga_arbiter
> cpu              hwrng      lp3           random  tty       tty19 tty3 
>  tty40  tty51  tty62  ttyS15  ttyS26  ttyS9    vcs3  vcsu1  vhci
> cpu_dma_latency  i2c-0      mapper        rfkill  tty0      tty2  tty30 
> tty41  tty52  tty63  ttyS16  ttyS27  udmabuf  vcs4  vcsu2  vhost-net
> cuse             input      mcelog        rtc     tty1      tty20 tty31 
> tty42  tty53  tty7   ttyS17  ttyS28  uhid     vcs5  vcsu3  vhost-vsock
> 
> 
> # tools/testing/selftests/vfio/scripts/setup.sh 0000:00:08.0
> 
> + echo "vfio-pci" > /sys/bus/pci/devices/0000:00:08.0/driver_override
> + echo "0000:00:08.0" > /sys/bus/pci/drivers/vfio-pci/bind
> tools/testing/selftests/vfio/scripts/lib.sh: line 9: echo: write error:
> Invalid argument    <--- the error is here.
> 
> 
> # lspci -vvv -s 0000:00:08.0
> 
> 00:08.0 Unclassified device [00ff]: Red Hat, Inc. QEMU PCI Test Device
>         Subsystem: Red Hat, Inc. QEMU Virtual Machine
>         Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr-
> Stepping- SERR+ FastB2B- DisINTx-
>         Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort-
> <TAbort- <MAbort- >SERR- <PERR- INTx-
>         Region 0: Memory at fea1f000 (32-bit, non-prefetchable) [size=4K]
>         Region 1: I/O ports at c000 [size=256]
> 
> Hi, Vipin
> 
> I worked with QEMU PCI Test Device. But the following error occur.
> 
> "tools/testing/selftests/vfio/scripts/lib.sh: line 9: echo: write error:
> Invalid argument"
> 
> Is this a known problem?
> 

Can you please check if you have passed iommu device in your QEMU
command? This is what I pass to my QEMU command

 -device intel-iommu,intremap=on,caching-mode=on,device-iotlb=on

Also, add the following to your guest kernel commandline

 intel_iommu=on

This should fix the issue you are seeing.

Alternatively, you can also enable noiommu mode in VFIO by executing:

  echo Y > /sys/module/vfio/parameters/enable_unsafe_noiommu_mode 

This should allow device to be bound to VFIO.

If none of the above approach works can you please share your QEMU
command and your guest VM /proc/cmdline.

Thanks
Vipin