ISM device firmware stores unique state information that can
can cause a wholesale unmap of the associated IOMMU (e.g. when
we get a termination signal for QEMU) to trigger firmware errors
because firmware believes we are attempting to invalidate entries
that are still in-use by the guest OS (when in fact that guest is
in the process of being terminated or rebooted).
To alleviate this, register both a shutdown notifier (for unexpected
termination cases e.g. virsh destroy) as well as a reset callback
(for cases like guest OS reboot).  For each of these scenarios, trigger
PCI device reset; this is enough to indicate to firmware that the IOMMU
is no longer in-use by the guest OS, making it safe to invalidate any
associated IOMMU entries.

Fixes: 15d0e794 ("s390x/pci: don't fence interpreted devices without MSI-X")
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Message-Id: <20221209195700.263824-1-mjrosato@linux.ibm.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
[thuth: Adjusted the hunk in s390-pci-vfio.c due to different context]
Signed-off-by: Thomas Huth <thuth@redhat.com>