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

[Zhu Yanjun <yanjun.zhu@linux.dev>]

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@linux.dev>

Zhu Yanjun

>
> Thanks
> Vipin

-- 
Best Regards,
Yanjun.Zhu