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

[Zhu Yanjun]

在 2026/8/4 23:02, Vipin Sharma 写道:
> On Tue, Aug 04, 2026 at 03:19:34PM -0700, Yanjun.Zhu wrote:
> > On 7/14/26 8:15 AM, Vipin Sharma wrote:
> > > 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
> > >
> > >    $ kexec ...   # NOTE: Exact method will be distro-dependent
> > >
> > >    $ tools/testing/selftests/vfio/scripts/setup.sh 0000:00:04.0
> > >    $ tools/testing/selftests/vfio/vfio_pci_liveupdate_kexec_test --stage 2 0000:00:04.0
> > Hi, Vipin
> >
> > Thanks a lot for your help. I followed your suggestion, vfio-pci setup can
> > work.
> I am glad your setup using virsh is working.
>
> > The followings are the test result. In the step 3, after kexec, there are
> > some fails. I am not sure if these are known problem or not.
> >
> > 1. Before kexec command
> >
> > + modprobe -v vfio-pci
> > + tools/testing/selftests/vfio/scripts/setup.sh 0000:00:04.0
> > + echo "vfio-pci" > /sys/bus/pci/devices/0000:00:04.0/driver_override
> > + echo "0000:00:04.0" > /sys/bus/pci/drivers/vfio-pci/bind
> > + tools/testing/selftests/vfio/vfio_pci_liveupdate_kexec_test --stage 1
> > 0000:00:04.0
> > Preserving device in session
> > Preserving memfd of size 0x40100000 in session
> > # [STAGE 1] Forking persistent child to hold sessions...
> > # [STAGE 1] Child PID: 1236. Resources are pinned.
> > # [STAGE 1] You may now perform kexec reboot.
> > + set +x
> >
> > 2. Run kexec command
> >
> > 3. After kexec command
> >
> > + echo "vfio-pci" > /sys/bus/pci/devices/0000:00:04.0/driver_override
> > + echo "0000:00:04.0" > /sys/bus/pci/drivers/vfio-pci/bind
> > Checking open(/dev/vfio/devices/vfio0) fails  <--- I can confirm that the
> > /dev/vfio/devices/vfio0 exists. But open this failed.
> This is correct output. Test is verifying that open should fail. If it
> didn't fail the ntest would have exited with an error. A preserved VFIO
> FD can only be retrived using Live Update session ioctls and not through
> usual VFIO dev path.
>
> > Checking ioctl(group_fd, VFIO_GROUP_GET_DEVICE_FD, "0000:00:04.0") fails
> > (vfio_type1_iommu)      <--- fails
> > Checking ioctl(group_fd, VFIO_GROUP_GET_DEVICE_FD, "0000:00:04.0") fails
> > (vfio_type1v2_iommu).  <--- fails
> > Checking ioctl(group_fd, VFIO_GROUP_GET_DEVICE_FD, "0000:00:04.0") fails
> > (iommufd_compat_type1)  <--- fails
> > Checking ioctl(group_fd, VFIO_GROUP_GET_DEVICE_FD, "0000:00:04.0") fails
> > (iommufd_compat_type1v2). <--- fails
> These are all correct output. Test is verifying that userspace should
> not be able to get VFIO device FD only through Live Update session
> ioctls and nothing else.
>
> > Retrieving memfd from LUO
> > Finishing the session before retrieving the device (should fail)
> > Retrieving the device FD from LUO
> > Finishing the session before binding to iommufd (should fail)
> > Binding the device to an iommufd and setting it up
> > Finishing the session
> This is shows VFIO FD is successfully retrived by Live Update ioctl.
>
> So, you saw expected output from successful test run. I will change
> the message getting printed to avoid confusion. I think current way of
> printing ".... fails" is confusing.

Thanks a lot. I have made tests in KVM. I can get the same test results.

Reviewed-and-tested-by: Zhu Yanjun <yanjun.zhu@xxxxxxxxx>

Zhu Yanjun

> Thanks
> Vipin

--
Best Regards,
Yanjun.Zhu