[v4,0/9] support in-order feature

  In latest virtio-spec, new feature bit VIRTIO_F_IN_ORDER was introduced.
When this feature has been negotiated, virtio driver will use
descriptors in ring order: starting from offset 0 in the table, and
wrapping around at the end of the table. Vhost devices will always use
descriptors in the same order in which they have been made available.
This can reduce virtio accesses to used ring.

Based on updated virtio-spec, this series realized IN_ORDER prototype
in virtio driver. Due to new [RT]x path added into selection, also add
two new parameters mrg_rx and in_order into virtio-user vdev parameters
list. This will allow user to configure feature bits thus can impact
[RT]x path selection.

Performance of virtio user with IN_ORDER feature:

    Platform: Purely
    CPU: Intel(R) Xeon(R) Platinum 8160 CPU @ 2.10GHz
    DPDK baseline: 18.05
    Setup: testpmd with vhost vdev + testpmd with virtio vdev

    +--------------+----------+----------+---------+
    |Vhost->Virtio |1 Queue   |2 Queues  |4 Queues |
    +--------------+----------+----------+---------+
    |Inorder       |12.0Mpps  |24.2Mpps  |26.0Mpps |
    |Normal        |12.1Mpps  |18.5Mpps  |18.9Mpps |
    +--------------+----------+----------+---------+
    
    +--------------+----------+----------------+---------+
    |Virtio->Vhost |1 Queue   |2 Queues        |4 Queues |
    +--------------+----------+----------------+---------+
    |Inorder       |13.8Mpps  |10.7 ~ 15.2Mpps |11.5Mpps |
    |Normal        |13.3Mpps  |9.8 ~ 14Mpps    |10.5Mpps |
    +--------------+----------+----------------+---------+
    
    +---------+----------+----------------+----------------+
    |Loopback |1 Queue   |2 Queues        |4 Queues        |
    +---------+----------+----------------+----------------+
    |Inorder  |7.4Mpps   |9.1 ~ 11.6Mpps  |10.5 ~ 11.3Mpps |
    +---------+----------+----------------+----------------+
    |Normal   |7.5Mpps   |7.7 ~ 9.0Mpps   |7.6 ~ 7.8Mpps   |
    +---------+----------+----------------+----------------+

v4:
- disable simple [RT]x function for ARM
- squash doc update into relevant patches
- fix git-check-log and checkpatch errors

v3:
- refine [RT]x function selection logic
- fix in-order mergeable packets index error
- combine unsupport mask patch
- doc virtio in-order update
- fix checkpatch error

v2:
- merge to latest dpdk-net-virtio 
- not use in_direct for normal xmit packets
- update available ring for each descriptor
- clean up IN_ORDER xmit function
- unmask feature bits when disabled in_order or mgr_rxbuf
- extract common part between IN_ORDER and normal functions
- update performance result

Marvin Liu (11):
  vhost: advertise support in-order feature

Marvin Liu (9):
  vhost: advertise support in-order feature
  net/virtio: add in-order feature bit definition
  net/virtio-user: add unsupported features mask
  net/virtio-user: add mrg-rxbuf and in-order vdev parameters
  net/virtio: free in-order descriptors before device start
  net/virtio: extract common part for in-order functions
  net/virtio: support in-order Rx and Tx
  net/virtio: add in-order Rx/Tx into selection
  net/virtio: advertise support in-order feature

 doc/guides/nics/virtio.rst                    |  27 +-
 drivers/net/virtio/virtio_ethdev.c            |  31 +-
 drivers/net/virtio/virtio_ethdev.h            |   7 +
 drivers/net/virtio/virtio_pci.h               |   8 +
 drivers/net/virtio/virtio_rxtx.c              | 639 ++++++++++++++++--
 .../net/virtio/virtio_user/virtio_user_dev.c  |  30 +-
 .../net/virtio/virtio_user/virtio_user_dev.h  |   4 +-
 drivers/net/virtio/virtio_user_ethdev.c       |  45 +-
 drivers/net/virtio/virtqueue.c                |   8 +
 drivers/net/virtio/virtqueue.h                |   2 +
 lib/librte_vhost/socket.c                     |   6 +
 lib/librte_vhost/vhost.h                      |  10 +-
 12 files changed, 732 insertions(+), 85 deletions(-)