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

[Thomas Huth]

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