[dpdk-dev] [PATCH v4 0/5] vhost: support selective datapath

[Zhihong Wang]

This patch set introduces support for selective datapath in DPDK vhost-user
lib. vDPA stands for vhost Data Path Acceleration. The idea is to support
virtio ring compatible devices to serve virtio driver directly to enable
datapath acceleration.

Design details
====

A vDPA device is a virtio ring compatible backend. It's defined as follows:

struct rte_vdpa_dev_addr {
	enum vdpa_addr_type type;
	union {
		uint8_t __dummy[64];
		struct rte_pci_addr pci_addr;
	};
};

struct rte_vdpa_dev_ops {
	vdpa_dev_queue_num_get_t  queue_num_get;
	vdpa_dev_feature_get_t    feature_get;
	vdpa_dev_feature_get_t    protocol_feature_get;
	vdpa_dev_conf_t           dev_conf;
	vdpa_dev_close_t          dev_close;
	vdpa_vring_state_set_t    vring_state_set;
	vdpa_feature_set_t        feature_set;
	vdpa_migration_done_t     migration_done;
	vdpa_get_vfio_group_fd_t  get_vfio_group_fd;
	vdpa_get_vfio_device_fd_t get_vfio_device_fd;
	vdpa_get_notify_area_t    get_notify_area;
};

struct rte_vdpa_device {
	struct rte_vdpa_dev_addr addr;
	struct rte_vdpa_dev_ops *ops;
} __rte_cache_aligned;


Changes to the current vhost-user lib are:
====

 1. Make vhost device capabilities configurable to adopt various devices.
    Such capabilities include supported features, protocol features, queue
    number. APIs are introduced to configure these capabilities.

 2. A set of device ops is defined for device specific operations:

     a. queue_num_get: Called to get supported queue number of the device.

     b. feature_get: Called to get supported features of the device.

     c. protocol_feature_get: Called to get supported protocol features of
        the device.

     d. dev_conf: Called to configure the actual device when the virtio
        device becomes ready.

     e. dev_close: Called to close the actual device when the virtio device
        is stopped.

     f. vring_state_set: Called to change the state of the vring in the
        actual device when vring state changes.

     g. feature_set: Called to set the negotiated features to device.

     h. migration_done: Called to allow the device to response to RARP
        sending.

     i. get_vfio_group_fd: Called to get the VFIO group fd of the device.

     j. get_vfio_device_fd: Called to get the VFIO device fd of the device.

     k. get_notify_area: Called to get the notify area info of the queue.

 3. To make vhost aware of its datapath type, an device id (did) is added
    into the vhost data structure to identify the actual device. APIs are
    introduced to configure it. When the default software datapath is used,
    did is set to -1. When alternative datapath is used, did should be set
    to specify which device to use, and each vhost-user socket can have
    only 1 connection in this case.

Working process:
====

 1. Register vDPA device with address and device ops, and get a did.

 2. For vhost device creation:

      a. Register vhost-user socket.

      b. Set did of the vhost-user socket.

      c. Register vhost-user callbacks.

      d. Start to wait for connection.

 3. When connection comes and virtio device data structure is negotiated,
    the device will be configured with all needed info.

---
Changes in v4:

 1. Remove the "engine" concept in the lib.

---
Changes in v3:

 1. Keep macro names the same as in the spec.

 2. Export new APIs where they're introduced.

---
Changes in v2:

 1. Ensure negotiated capabilities are supported in vhost-user lib.

 2. Add APIs for live migration.

 3. Configure the data path at the right time.

 4. Add VFIO related vDPA device ops.

 5. Rebase on dpdk-next-virtio.

Zhihong Wang (5):
  vhost: export vhost feature definitions
  vhost: support selective datapath
  vhost: add apis for datapath configuration
  vhost: adapt vhost lib for selective datapath
  vhost: add apis for live migration

 lib/librte_vhost/Makefile              |   4 +-
 lib/librte_vhost/rte_vdpa.h            |  94 ++++++++++++++++++++++
 lib/librte_vhost/rte_vhost.h           | 143 +++++++++++++++++++++++++++++++++
 lib/librte_vhost/rte_vhost_version.map |  14 ++++
 lib/librte_vhost/socket.c              | 130 ++++++++++++++++++++++++++++--
 lib/librte_vhost/vdpa.c                |  96 ++++++++++++++++++++++
 lib/librte_vhost/vhost.c               |  91 +++++++++++++++++++++
 lib/librte_vhost/vhost.h               |  13 ++-
 lib/librte_vhost/vhost_user.c          |  54 +++++++++++--
 lib/librte_vhost/vhost_user.h          |   7 --
 10 files changed, 625 insertions(+), 21 deletions(-)
 create mode 100644 lib/librte_vhost/rte_vdpa.h
 create mode 100644 lib/librte_vhost/vdpa.c

-- 
2.13.6