[v2,0/1] integrate dmadev in vhost

  Since dmadev is introduced in 21.11, to avoid the overhead of vhost DMA
abstraction layer and simplify application logics, this patch integrates
dmadev in vhost.

To enable the flexibility of using DMA devices in different function
modules, not limited in vhost, vhost doesn't manage DMA devices.
Applications, like OVS, need to manage and configure DMA devices and
tell vhost what DMA device to use in every dataplane function call.

In addition, vhost supports M:N mapping between vrings and DMA virtual
channels. Specifically, one vring can use multiple different DMA channels
and one DMA channel can be shared by multiple vrings at the same time.
The reason of enabling one vring to use multiple DMA channels is that
it's possible that more than one dataplane threads enqueue packets to
the same vring with their own DMA virtual channels. Besides, the number
of DMA devices is limited. For the purpose of scaling, it's necessary to
support sharing DMA channels among vrings.

As only enqueue path is enabled DMA acceleration, the new dataplane
functions are like:
1). rte_vhost_submit_enqueue_burst(vid, queue_id, pkts, count, dma_id,
    dma_vchan):
    Get descriptors and submit copies to DMA virtual channel for the
    packets that need to be send to VM.
 
2). rte_vhost_poll_enqueue_completed(vid, queue_id, pkts, count, dma_id,
    dma_vchan):
    Check completed DMA copies from the given DMA virtual channel and
    write back corresponding descriptors to vring.

OVS needs to call rte_vhost_poll_enqueue_completed to clean in-flight
copies on previous call and it can be called inside rxq_recv function,
so that it doesn't require big change in OVS datapath. For example:
netdev_dpdk_vhost_rxq_recv() {
	...
	qid = rxq->queue_id * VIRTIO_QNUM + VIRTIO_RXQ;
	rte_vhost_poll_enqueue_completed(vid, qid, ...);
}

Change log
==========
v1 -> v2:
- add SW fallback if rte_dma_copy() reports error
- print error if rte_dma_completed() reports error
- add poll_factor while call rte_dma_completed() for scatter-gaher packets
- use trylock instead of lock in rte_vhost_poll_enqueue_completed()
- check if dma_id and vchan_id valid
- input dma_id in rte_vhost_async_dma_configure()
- remove useless code, brace and hardcode in vhost example
- redefine MAX_VHOST_DEVICE to RTE_MAX_VHOST_DEVICE
- update doc and comments
rfc -> v1:
- remove useless code
- support dynamic DMA vchannel ring size (rte_vhost_async_dma_configure)
- fix several bugs
- fix typo and coding style issues
- replace "while" with "for"
- update programmer guide 
- support share dma among vhost in vhost example
- remove "--dma-type" in vhost example

Jiayu Hu (1):
  vhost: integrate dmadev in asynchronous datapath

 doc/guides/prog_guide/vhost_lib.rst |  95 ++++-----
 examples/vhost/Makefile             |   2 +-
 examples/vhost/ioat.c               | 218 --------------------
 examples/vhost/ioat.h               |  63 ------
 examples/vhost/main.c               | 255 ++++++++++++++++++-----
 examples/vhost/main.h               |  11 +
 examples/vhost/meson.build          |   6 +-
 lib/vhost/meson.build               |   2 +-
 lib/vhost/rte_vhost.h               |   2 +
 lib/vhost/rte_vhost_async.h         | 132 +++++-------
 lib/vhost/version.map               |   3 +
 lib/vhost/vhost.c                   | 148 ++++++++++----
 lib/vhost/vhost.h                   |  64 +++++-
 lib/vhost/vhost_user.c              |   2 +
 lib/vhost/virtio_net.c              | 305 +++++++++++++++++++++++-----
 15 files changed, 744 insertions(+), 564 deletions(-)
 delete mode 100644 examples/vhost/ioat.c
 delete mode 100644 examples/vhost/ioat.h