Manual Pages  — IBV_BIND_MW

ibv_bind_mw - post a request to bind a type 1 memory window to a memory region

SYNOPSIS DESCRIPTION RETURN VALUE NOTES SEE ALSO AUTHORS

#include <infiniband/verbs.h> 

int ibv_bind_mw(struct ibv_qp *qp, struct ibv_mw *mw", 
                struct ibv_mw_bind *mw_bind"); 

ibv_bind_mw() posts to the queue pair qp a request to bind the memory window mw according to the details in mw_bind.

The argument mw_bind is an ibv_mw_bind struct, as defined in <infiniband/verbs.h>.

struct ibv_mw_bind {
uint64_t                     wr_id;           /* User defined WR ID */
int                          send_flags;      /* Use ibv_send_flags */
struct ibv_mw_bind_info      bind_info;       /* MW bind information */
}

struct ibv_mw_bind_info {
struct ibv_mr                *mr;             /* The MR to bind the MW to */
uint64_t                     addr;            /* The address the MW should start at */
uint64_t                     length;          /* The length (in bytes) the MW should span */
int                          mw_access_flags; /* Access flags to the MW. Use ibv_access_flags */
};

The QP Transport Service Type must be either UC, RC or XRC_SEND for bind operations.

The attribute send_flags describes the properties of the WR. It is either 0 or the bitwise OR of one or more of the following flags:

IBV_SEND_FENCE Set the fence indicator.
IBV_SEND_SIGNALED Set the completion notification indicator. Relevant only if QP was created with sq_sig_all=0
The mw_access_flags define the allowed access to the MW after the bind completes successfully. It is either 0 or the bitwise OR of one or more of the following flags:
IBV_ACCESS_REMOTE_WRITE Enable Remote Write Access. Requires local write access to the MR.
IBV_ACCESS_REMOTE_READ Enable Remote Read Access
IBV_ACCESS_REMOTE_ATOMIC Enable Remote Atomic Operation Access (if supported). Requires local write access to the MR.
IBV_ACCESS_ZERO_BASED If set, the address set on the 'remote_addr' field on the WR will be an offset from the MW's start address.

ibv_bind_mw() returns 0 on success, or the value of errno on failure (which indicates the failure reason). In case of a success, the R_key of the memory window after the bind is returned in the mw_bind->mw->rkey field.

The bind does not complete when the function return - it is merely posted to the QP. The user should keep a copy of the old R_key, and fix the mw structure if the subsequent CQE for the bind operation indicates a failure. The user may safely send the R_key using a send request on the same QP, (based on QP ordering rules: a send after a bind request on the same QP are always ordered), but must not transfer it to the remote in any other manner before reading a successful CQE.

Note that for type 2 MW, one should directly post bind WR to the QP, using ibv_post_send.

Majd Dibbiny <majd@mellanox.com>