vhost: support async dequeue data path

From: Xuan Ding <[email protected]>

The presence of asynchronous path allows applications to offload memory copies to DMA engine, so as to save CPU cycles and improve the copy performance. This patch set implements vhost async dequeue data path for split ring. The code is based on latest enqueue changes [1].

This patch set is a new design and implementation of [2]. Since dmadev was introduced in DPDK 21.11, to simplify application logics, this patch integrates dmadev in vhost. With dmadev integrated, 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.

A new asynchronous dequeue function is introduced:
1) rte_vhost_async_try_dequeue_burst(int vid, uint16_t queue_id, struct rte_mempool *mbuf_pool, struct rte_mbuf **pkts, uint16_t count, int *nr_inflight,
uint16_t dma_id, uint16_t vchan_id)

Receive packets from the guest and offloads copies to DMA
virtual channel.

[1] https://mails.dpdk.org/archives/dev/2022-February/234555.html
[2] https://mails.dpdk.org/archives/dev/2021-September/218591.html

v7->v8:
* change dma_id to int16_t
* refine API documentation

v6->v7:
* correct code formatting
* change some functions to inline

v5->v6:
* adjust EXPERIMENTAL header

v4->v5:
* rebase to latest DPDK
* add some checks

v3->v4:
* fix CI build warnings
* adjust some indentation
* pass vq instead of queue_id

v2->v3:
* fix mbuf not updated correctly for large packets

v1->v2:
* fix a typo
* fix a bug in desc_to_mbuf filling

RFC v3 -> v1:
* add sync and async path descriptor to mbuf refactoring
* add API description in docs

RFC v2 -> RFC v3:
* rebase to latest DPDK version

RFC v1 -> RFC v2:
* fix one bug in example
* rename vchan to vchan_id
* check if dma_id and vchan_id valid
* rework all the logs to new standard

Xuan Ding (5):
vhost: prepare sync for descriptor to mbuf refactoring
vhost: prepare async for descriptor to mbuf refactoring
vhost: merge sync and async descriptor to mbuf filling
vhost: support async dequeue for split ring examples/vhost: support async dequeue data path

 doc/guides/prog_guide/vhost_lib.rst    |   6 +
 doc/guides/rel_notes/release_22_07.rst |   5 +
 doc/guides/sample_app_ug/vhost.rst     |   9 +-
 examples/vhost/main.c                  | 286 ++++++++++-----
 examples/vhost/main.h                  |  32 +-
 examples/vhost/virtio_net.c            |  16 +-
 lib/vhost/rte_vhost_async.h            |  37 ++
 lib/vhost/version.map                  |   2 +-
 lib/vhost/vhost.h                      |   1 +
 lib/vhost/virtio_net.c                 | 473 ++++++++++++++++++++++---
 10 files changed, 715 insertions(+), 152 deletions(-)

2.17.1