We've seen a request for CI and development to have access to migratable
vfio devices without any specific hardware requirements.  One way to do
that is to enable migration support on the mtty mdev sample driver, as
done here.

This device is particularly easy to migrate because it doesn't actually
do DMA, or in fact much of anything.  Therefore we can claim P2P and
dirty logging as well.  PRE_COPY support is also included in a similar
fashion to hisi_acc.  This provides early compatibility testing, which
is probably over-done, but perhaps illustrates good practice with
matching data stream magic, versioning, and feature flags.  These might
later be used for backwards compatibility, particularly since I'm not
positive that copying the struct serial_port between source and
destination is sufficient.

Along the way, testing migration where the source and target are
incompatible, I fixed an eventfd leak.  Thanks,

Alex

Alex Williamson (2):
  vfio/mtty: Fix eventfd leak
  vfio/mtty: Enable migration support

 samples/vfio-mdev/mtty.c | 610 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 605 insertions(+), 5 deletions(-)

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2.40.1