Re: [PATCH] hw/virtio: Add a protection against duplicate vu_scmi_stop calls

[Thomas Huth <thuth@redhat.com>]

On 03/08/2023 11.50, Michael S. Tsirkin wrote:
> On Thu, Aug 03, 2023 at 09:38:20AM +0200, Thomas Huth wrote:
>> On 03/08/2023 09.10, Milan Zamazal wrote:
>>> Fabiano Rosas <farosas@suse.de> writes:
>>>
>>>> Milan Zamazal <mzamazal@redhat.com> writes:
>>>>
>>>>> The QEMU CI fails in virtio-scmi test occasionally.  As reported by
>>>>> Thomas Huth, this happens most likely when the system is loaded and it
>>>>> fails with the following error:
>>>>>
>>>>>     qemu-system-aarch64: ../../devel/qemu/hw/pci/msix.c:659:
>>>>>     msix_unset_vector_notifiers: Assertion
>>>>> `dev->msix_vector_use_notifier && dev->msix_vector_release_notifier'
>>>>> failed.
>>>>>     ../../devel/qemu/tests/qtest/libqtest.c:200: kill_qemu() detected
>>>>> QEMU death from signal 6 (Aborted) (core dumped)
>>>>>
>>>>> As discovered by Fabiano Rosas, the cause is a duplicate invocation of
>>>>> msix_unset_vector_notifiers via duplicate vu_scmi_stop calls:
>>>>>
>>>>>     msix_unset_vector_notifiers
>>>>>     virtio_pci_set_guest_notifiers
>>>>>     vu_scmi_stop
>>>>>     vu_scmi_disconnect
>>>>>     ...
>>>>>     qemu_chr_write_buffer
>>>>>
>>>>>     msix_unset_vector_notifiers
>>>>>     virtio_pci_set_guest_notifiers
>>>>>     vu_scmi_stop
>>>>>     vu_scmi_set_status
>>>>>     ...
>>>>>     qemu_cleanup
>>>>>
>>>>> While vu_scmi_stop calls are protected by vhost_dev_is_started()
>>>>> check, it's apparently not enough.  vhost-user-blk and vhost-user-gpio
>>>>> use an extra protection, see f5b22d06fb (vhost: recheck dev state in
>>>>> the vhost_migration_log routine) for the motivation.  Let's use the
>>>>> same in vhost-user-scmi, which fixes the failure above.
>>>>>
>>>>> Fixes: a5dab090e142 ("hw/virtio: Add boilerplate for vhost-user-scmi device")
>>>>> Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
>>>>
>>>> Reviewed-by: Fabiano Rosas <farosas@suse.de>
>>>
>>> Please note that this bug fix should IMO definitely go to 8.1, to not
>>> have a bug in vhost-user-scmi and to not have broken tests.  Any chance
>>> to get it merged?
>>
>> If nobody else is planning a pull request with this patch included, I can
>> take it for my next PR (since it is fixing the CI, I just saw another
>> failure here:
>> https://gitlab.com/qemu-project/qemu/-/jobs/4790457938#L4784 )
>>
>>   Thomas
>>
> 
> I picked it up but if you like I can drop it.

I think it better fits into your tree, so if you plan a PR before the next 
RC, then please go ahead. I'll drop it from my branch again.

  Thomas