######版本為linux4.13.2#########
virtio_init
bus_register(&virtio_bus)
static struct bus_type virtio_bus = {
.name = "virtio",
.match = virtio_dev_match,
.dev_groups = virtio_dev_groups,
.uevent = virtio_uevent,
.probe = virtio_dev_probe,
.remove = virtio_dev_remove,
};
virtio_dev_probe //virtio bus的probe
virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER) //發現virtio驅動
dev->config->set_status(dev, dev->config->get_status(dev) | status);
virtio_finalize_features
virtio_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK) //features ok
drv->probe(dev) //調用驅動的probe，比如virtio net的 virtnet_probe
virtio_device_ready //設定VIRTIO_CONFIG_S_DRIVER_OK
virtio_config_enable //配置使能
-----------
//virtio net前端驅動入口
virtio_net_driver_init
register_virtio_driver(&virtio_net_driver)
driver_register
bus_add_driver
driver_attach //bus_for_each_dev(drv->bus, NULL, drv, __driver_attach)
__driver_attach
driver_probe_device
really_probe
dev->bus->probe(dev) 或 drv->probe //一般bus的probe裡會調用drv的probe
省略掉device的probe，這裡驅動在注冊時也會調用probe（這裡最好把device的probe分析下，不然始終沒連接配接起來！）
static struct virtio_driver virtio_net_driver = {
.feature_table = features,
.feature_table_size = ARRAY_SIZE(features),
.feature_table_legacy = features_legacy,
.feature_table_size_legacy = ARRAY_SIZE(features_legacy),
.driver.name = KBUILD_MODNAME,
.driver.owner = THIS_MODULE,
.id_table = id_table,
.validate = virtnet_validate,
.probe = virtnet_probe,
.remove = virtnet_remove,
.config_changed = virtnet_config_changed,
#ifdef CONFIG_PM_SLEEP
.freeze = virtnet_freeze,
.restore = virtnet_restore,
#endif
};
virtnet_probe
dev->netdev_ops = &virtnet_netdev; //此ops回調結構體包含了open、stop、start_xmit、set_mac_address、poll_controller等
dev->ethtool_ops = &virtnet_ethtool_ops; //ethtool的ops
INIT_WORK(&vi->config_work, virtnet_config_changed_work); //配置改變工作隊列
init_vqs
virtnet_alloc_queues
INIT_DELAYED_WORK(&vi->refill, refill_work); //後面會用到，用于延時填充avail ring
netif_napi_add //添加virtnet_poll到rq[i].napi
netif_tx_napi_add //添加virtnet_poll_tx到sq[i].napi
sg_init_table
virtnet_find_vqs
callbacks[rxq2vq(i)] = skb_recv_done; //接收回調
callbacks[txq2vq(i)] = skb_xmit_done; //發送回調
vi->vdev->config->find_vqs(XXX,callbacks,XXX) //回調指派，中斷中會調用此回調
//填充avail ring
refill_work
//接收回調
skb_recv_done
virtqueue_napi_schedule
virtnet_poll
//接收處理napi
virtnet_poll
virtnet_poll_cleantx
virtnet_receive
{virtqueue_get_buf
virtqueue_get_buf_ctx //從vring used中取出id、len；從desc_state中取出data？(在virtqueue_add 的時候會進行指派)
detach_buf //釋放相關記憶體及指針,這裡會有num_free++操作(空閑buffer數，已經處理後釋放的buffer數)
receive_buf
receive_small[receive_big、receive_mergeable]
build_skb
skb_vnet_hdr
virtio_net_hdr_to_skb
napi_gro_receive //送給上層處理
} //循環處理完所有used ring包
try_fill_recv //條件是：空閑vring數量大于一半；如果失敗會啟動delaywork
try_fill_recv 添加buffer。主要在receiving路徑被調用；也可以在receiving之前的ndo_open中；另一個場景是refill_work（利用napi_disable來關閉receiving）
{add_recvbuf_mergeable
add_recvbuf_big
add_recvbuf_small
virtqueue_add_inbuf
virtqueue_add //添加一個buffer到avail ring
}//循環，每次添加一個，知道把空閑的buffer添加滿！
virtqueue_kick //notify
virtqueue_kick_prepare
vring_need_event
return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old);//簡化後就是event_idx+1>old；而event_idx是記錄後端處理位置；意思就是後端處理位置超過（加1後超過，其實是等于）了上次添加buffer的位置，就傳回真，需要新添加buffer
//沒用event的場景看vring.used->flags判斷是否notify
virtqueue_notify
調用其的函數有：
refill_work //用work隊列延時填
virtnet_receive《- virtnet_poll《-virtnet_alloc_queues（netif_napi_add）《- virtnet_netpoll（napi_schedule）《-virtnet_netdev.ndo_poll_controller《-netpoll_poll_dev（ops->ndo_poll_controller）//《-netpoll_send_skb_on_dev《-netpoll_send_skb《-netpoll_send_udp（貌似跟丢了,反正是在napi中調用）
調用try_fill_recv條件：if (rq->vq->num_free > virtqueue_get_vring_size(rq->vq) / 2)；vq->num_free為空閑的vring數量（vring_num-avail_num）；即空閑vring數量大于一半時就觸發添加。
virtnet_open
virtnet_restore_up
總結：guest中virtio網卡驅動在napi中調用接收函數中判斷是否應該添加buffer到vring中。當空閑vring數量大于一半時，會調用try_fill_recv來試圖添加buffer，因為還得滿足vring_need_event條件；如果try_fill_recv失敗會利用schedule_delayed_work來延時再調用。pci中斷處理程式中會調用，virtio net注冊的回調，進而調用napi來處理接收。
------------------------
//發送處理napi
virtnet_poll_tx
//發送回調
skb_xmit_done
=========================
module_pci_driver(virtio_pci_driver)
module_driver(__pci_driver, pci_register_driver, pci_unregister_driver) //驅動注冊宏
pci_register_driver
__pci_register_driver
drv->driver.bus = &pci_bus_type;
driver_register
struct bus_type pci_bus_type = {
.name = "pci",
.match = pci_bus_match,
.uevent = pci_uevent,
.probe = pci_device_probe,
.remove = pci_device_remove,
.shutdown = pci_device_shutdown,
.dev_groups = pci_dev_groups,
.bus_groups = pci_bus_groups,
.drv_groups = pci_drv_groups,
.pm = PCI_PM_OPS_PTR,
.num_vf = pci_bus_num_vf,
};
pci_device_probe
__pci_device_probe
pci_call_probe
local_pci_probe
pci_drv->probe //這裡會調用virtio_pci_driver的probe(virtio_pci_probe)
//virtio pci驅動入口
virtio_pci_probe
virtio_pci_legacy_probe
vp_dev->ioaddr = pci_iomap(pci_dev, 0, 0) //通過device映射io位址
vp_dev->isr = vp_dev->ioaddr + VIRTIO_PCI_ISR //擷取isr中斷寄存器位址
vp_dev->vdev.config = &virtio_pci_config_ops //包含vp的set、get、vp_find_vqs等
vp_dev->config_vector = vp_config_vector
vp_dev->setup_vq = setup_vq
[virtio_pci_modern_probe]
register_virtio_device
device_register
vp_find_vqs //config->find_vqs
vp_find_vqs_msix //軟中斷？
vp_request_msix_vectors
request_irq(XXX,vp_config_changed,XXX) //pci配置改變中斷
request_irq(XXX,vp_vring_interrupt,XXX) //pci硬體中斷？
vp_setup_vq
vp_dev->setup_vq
request_irq(XXX,vring_interrupt,XXX) //pci硬體中斷？
[vp_find_vqs_intx] //正常中斷，就一個
request_irq(XXX,vp_interrupt,XXX)
vp_setup_vq
vp_dev->setup_vq
vp_config_vector //設定VIRTIO_MSI_CONFIG_VECTOR寄存器，用來做msi軟中斷？
setup_vq
vring_create_virtqueue
vring_init
__vring_new_virtqueue
vring_interrupt
more_used //
vq->vq.callback //調用virtqueue的接受或發送回調
vp_config_changed
virtio_config_changed
__virtio_config_changed
drv->config_changed
vp_vring_interrupt
vring_interrupt
vp_interrupt
ioread8(vp_dev->isr) //讀清isr
vp_config_changed
vp_vring_interrupt
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