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

[Thomas Huth <thuth@redhat.com>]

On 20/07/2023 12.10, Milan Zamazal wrote:
> 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>
> ---
>   hw/virtio/vhost-user-scmi.c         | 7 +++++++
>   include/hw/virtio/vhost-user-scmi.h | 1 +
>   2 files changed, 8 insertions(+)

Thanks, that fixes the problem for me!

Tested-by: Thomas Huth <thuth@redhat.com>