参考http://hustcat.github.io/linux-soft-roce-implementation/
队列初始化
libRXE (user space library)
ibv_create_qp
|--- rxe_create_qp
|--- ibv_cmd_create_qp
- ibv_create_qp
LATEST_SYMVER_FUNC(ibv_create_qp, 1_1, "IBVERBS_1.1",
struct ibv_qp *,
struct ibv_pd *pd,
struct ibv_qp_init_attr *qp_init_attr)
{
struct ibv_qp *qp = pd->context->ops.create_qp(pd, qp_init_attr); ///rxe_ctx_ops
///..
}
- rxe_create_qp
static struct ibv_qp *rxe_create_qp(struct ibv_pd *pd,
struct ibv_qp_init_attr *attr)
{
struct ibv_create_qp cmd;
struct rxe_create_qp_resp resp;
struct rxe_qp *qp;
int ret;
////..
ret = ibv_cmd_create_qp(pd, &qp->ibv_qp, attr, &cmd, sizeof cmd,
&resp.ibv_resp, sizeof resp); /// ibv_create_qp CMD, to kernel
///...
qp->sq.max_sge = attr->cap.max_send_sge;
qp->sq.max_inline = attr->cap.max_inline_data;
qp->sq.queue = mmap(NULL, resp.sq_mi.size, PROT_READ | PROT_WRITE,
MAP_SHARED,
pd->context->cmd_fd, resp.sq_mi.offset); ///mmap，参考rxe_mmap
ibv_context->cmd_fd指向对应的ibv_device，由ibv_open_device返回。
ibv_cmd_create_qp会通过ibv_context->cmd_fd给内核发送IB_USER_VERBS_CMD_CREATE_QP命令，参考libiverbs@ibv_cmd_create_qp.
对应的内核write函数为ib_uverbs_write:
///drivers/infiniband/core/uverbs_main.c
static const struct file_operations uverbs_fops = {
.owner = THIS_MODULE,
.write = ib_uverbs_write,
.open = ib_uverbs_open,
.release = ib_uverbs_close,
.llseek = no_llseek,
};
- ibv_open_device
///libibverbs/device.c
LATEST_SYMVER_FUNC(ibv_open_device, 1_1, "IBVERBS_1.1",
struct ibv_context *,
struct ibv_device *device)
{
struct verbs_device *verbs_device = verbs_get_device(device);
char *devpath;
int cmd_fd, ret;
struct ibv_context *context;
struct verbs_context *context_ex;
if (asprintf(&devpath, "/dev/infiniband/%s", device->dev_name) < 0)
return NULL;
/*
* We'll only be doing writes, but we need O_RDWR in case the
* provider needs to mmap() the file.
*/
cmd_fd = open(devpath, O_RDWR | O_CLOEXEC); /// /dev/infiniband/uverbs0
free(devpath);
if (cmd_fd < 0)
return NULL;
if (!verbs_device->ops->init_context) {
context = verbs_device->ops->alloc_context(device, cmd_fd); ///rxe_alloc_context, rxe_dev_ops
if (!context)
goto err;
}
///...
context->device = device;
context->cmd_fd = cmd_fd;
pthread_mutex_init(&context->mutex, NULL);
ibverbs_device_hold(device);
return context;
///...
}
kernel (rdma_rxe module)
- ib_uverbs_create_qp
IB_USER_VERBS_CMD_CREATE_QP的处理函数为函数ib_uverbs_create_qp.
ib_uverbs_write
|--- ib_uverbs_create_qp
|--- create_qp
|--- ib_device->create_qp
|--- rxe_create_qp
create_qp调用ib_device->create_qp,对于RXE， 为函数rxe_create_qp， 参考rxe_register_device.
- rxe_create_qp
rxe_create_qp
|--- rxe_qp_from_init
|--- rxe_qp_init_req
rxe_qp_from_init完成发送队列和接收队列的初始化。
- rxe_qp_init_req
rxe_qp_init_req主要做以下一些事情：
创建对应的UDP socket
调用
rxe_queue_init完成发送队列的初始化.初始化对应的tasklet
- rxe_queue_init
rxe_queue_init给队列分配内存空间：
struct rxe_queue *rxe_queue_init(struct rxe_dev *rxe,
int *num_elem,
unsigned int elem_size)
{
struct rxe_queue *q;
size_t buf_size;
unsigned int num_slots;
///...
buf_size = sizeof(struct rxe_queue_buf) + num_slots * elem_size;
q->buf = vmalloc_user(buf_size);
///...
}
rxe_queue->buf指向的内存缓冲区，由rxe_mmap映射到用户空间，队列的element对应数据结构struct rxe_send_wqe.
libiverbs API调用ibv_post_send时，会将对应的struct rxe_send_wqe加入到该队列，参考rdma-core@post_one_send.
- rxe_mmap
/**
* rxe_mmap - create a new mmap region
* @context: the IB user context of the process making the mmap() call
* @vma: the VMA to be initialized
* Return zero if the mmap is OK. Otherwise, return an errno.
*/
int rxe_mmap(struct ib_ucontext *context, struct vm_area_struct *vma)
{
struct rxe_dev *rxe = to_rdev(context->device);
unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
unsigned long size = vma->vm_end - vma->vm_start;
struct rxe_mmap_info *ip, *pp;
///...
found_it:
list_del_init(&ip->pending_mmaps);
spin_unlock_bh(&rxe->pending_lock);
ret = remap_vmalloc_range(vma, ip->obj, 0);
if (ret) {
pr_err("rxe: err %d from remap_vmalloc_range\n", ret);
goto done;
}
vma->vm_ops = &rxe_vm_ops;
vma->vm_private_data = ip;
rxe_vma_open(vma);
///...
}
发送数据
libRXE
rxe_post_send会将struct ibv_send_wr转成struct rxe_send_wqe，并加入到发送队列rxe_qp->rq，然后通过cmd_fd给RXE内核模块发送IB_USER_VERBS_CMD_POST_SEND命令：
///providers/rxe/rxe.c
/* this API does not make a distinction between
restartable and non-restartable errors */
static int rxe_post_send(struct ibv_qp *ibqp,
struct ibv_send_wr *wr_list,
struct ibv_send_wr **bad_wr)
{
int rc = 0;
int err;
struct rxe_qp *qp = to_rqp(ibqp);/// ibv_qp -> rxe_qp
struct rxe_wq *sq = &qp->sq;
if (!bad_wr)
return EINVAL;
*bad_wr = NULL;
if (!sq || !wr_list || !sq->queue)
return EINVAL;
pthread_spin_lock(&sq->lock);
while (wr_list) {
rc = post_one_send(qp, sq, wr_list); /// ibv_send_wr -> rxe_send_wqe, enqueue
if (rc) {
*bad_wr = wr_list;
break;
}
wr_list = wr_list->next;
}
pthread_spin_unlock(&sq->lock);
err = post_send_db(ibqp); /// IB_USER_VERBS_CMD_POST_SEND cmd
return err ? err : rc;
}
kernel
处理的IB_USER_VERBS_CMD_POST_SEND的函数为ib_uverbs_post_send:
ib_uverbs_post_send -> ib_device->post_send -> rxe_post_send -> rxe_requester -> ip_local_out。
- rxe_post_send
static int rxe_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
struct ib_send_wr **bad_wr)
{
int err = 0;
struct rxe_qp *qp = to_rqp(ibqp); ///ib_qp -> rxe_qp
///...
/*
* Must sched in case of GSI QP because ib_send_mad() hold irq lock,
* and the requester call ip_local_out_sk() that takes spin_lock_bh.
*/
must_sched = (qp_type(qp) == IB_QPT_GSI) ||
(queue_count(qp->sq.queue) > 1);
rxe_run_task(&qp->req.task, must_sched); /// to rxe_requester
return err;
}
- rxe_requester
rxe_requester从rxe_qp队列取出rxe_send_wqe，生成对应的skb_buff，然后下发给对应的rxe_dev设备：
///sw/rxe/rxe_req.c
int rxe_requester(void *arg)
{
struct rxe_qp *qp = (struct rxe_qp *)arg;
struct rxe_pkt_info pkt;
struct sk_buff *skb;
struct rxe_send_wqe *wqe;
///...
wqe = req_next_wqe(qp); /// get rxe_send_wqe
///...
/// rxe_send_wqe -> skb
skb = init_req_packet(qp, wqe, opcode, payload, &pkt);
///...
ret = rxe_xmit_packet(to_rdev(qp->ibqp.device), qp, &pkt, skb);
///...
}
static inline int rxe_xmit_packet(struct rxe_dev *rxe, struct rxe_qp *qp,
struct rxe_pkt_info *pkt, struct sk_buff *skb)
{
///...
if (pkt->mask & RXE_LOOPBACK_MASK) {
memcpy(SKB_TO_PKT(skb), pkt, sizeof(*pkt));
err = rxe->ifc_ops->loopback(skb);
} else {
err = rxe->ifc_ops->send(rxe, pkt, skb);/// ifc_ops->send, send
}
///...
}
ifc_ops->send最后会调用ip_local_out，从对应的物理NIC发送出去。
