[PATCH 0/7] Add VIRTIO_F_IN_ORDER support to vhost shadow virtqueue

["Eugenio Pérez" <eperezma@redhat.com>]

This series adds support for the VIRTIO_F_IN_ORDER feature flag to vhost shadow
virtqueue (SVQ), enabling migration of vDPA devices that offer this feature.
As SVQ acts as a virtio driver, the series follows the Linux kernel
implementation for the feature by Jason Wang.  This enables the live migration
of vhost-vdpa devices that supports IN_ORDER.

The IN_ORDER feature allows virtio devices to use many descriptors in batch,
just by marking the last one of the set as used.

The series is structured in three parts.  First, max_steps calculation in
virtqueue_ordered_fill is fixed to allow filling the entire virtqueue at once.
Otherwise, a full queue cannot be used with just one used entry.

Afterwards, the series extracts helper functions for descriptor processing to
prepare for in order changes:

Finally, the series adds IN_ORDER support, first adding conditional logic for
in-order vs regular processing and whitelisting the feature flag in SVQ.

Eugenio Pérez (7):
  virtio: Allow to fill a whole virtqueue in order
  vhost: move svq next desc array to descs state struct
  vhost: factor out the descriptor next fetching
  vhost: factor out the get of last used desc in SVQ
  vhost: factor out the detach buf logic in SVQ
  vhost: add in_order feature to shadow virtqueue
  vhost: accept in order feature flag

 hw/virtio/vhost-shadow-virtqueue.c | 215 +++++++++++++++++++++++++----
 hw/virtio/vhost-shadow-virtqueue.h |  38 ++++-
 hw/virtio/virtio.c                 |   2 +-
 3 files changed, 219 insertions(+), 36 deletions(-)

-- 
2.53.0