IBV_ALLOC_MW(3)        Libibverbs Programmer's Manual        IBV_ALLOC_MW(3)

NAME         top

       ibv_alloc_mw, ibv_dealloc_mw - allocate or deallocate a memory window

SYNOPSIS         top

       #include <infiniband/verbs.h>

       struct ibv_mw *ibv_alloc_mw(struct ibv_pd *pd,
                                   enum ibv_mw_type type);

       int ibv_dealloc_mw(struct ibv_mw *mw);

DESCRIPTION         top

       ibv_alloc_mw() allocates a memory window (MW) associated with the
       protection domain pd.  The MW's type (1 or 2A/2B) is type.

       The MW is created not bound. For it to be useful, the MW must be
       bound, through either ibv_bind_mw (type 1) or a special WR (type 2).
       Once bound, the memory window allows RDMA (remote) access to a subset
       of the MR to which it was bound, until invalidated by: ibv_bind_mw
       verb with zero length for type 1,
       IBV_WR_LOCAL_INV/IBV_WR_SEND_WITH_INV WR opcode for type 2,

       ibv_dealloc_mw() Unbinds in case was previously bound and deallocates
       the MW mw.

RETURN VALUE         top

       ibv_alloc_mw() returns a pointer to the allocated MW, or NULL if the
       request fails.  The remote key (R_Key) field rkey is used by remote
       processes to perform Atomic and RDMA operations. This key will be
       changed during bind operations. The remote process places this rkey
       as the rkey field of struct ibv_send_wr passed to the ibv_post_send

       ibv_dealloc_mw() returns 0 on success, or the value of errno on
       failure (which indicates the failure reason).

NOTES         top

       ibv_dereg_mr() fails if any memory window is still bound to this MR.

SEE ALSO         top

       ibv_alloc_pd(3), ibv_post_send(3), ibv_bind_mw(3), ibv_reg_mr(3),

AUTHORS         top

       Majd Dibbiny <>

       Yishai Hadas <>

COLOPHON         top

       This page is part of the rdma-core (RDMA Core Userspace Libraries and
       Daemons) project.  Information about the project can be found at 
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libibverbs                       2016-02-02                  IBV_ALLOC_MW(3)

Pages that refer to this page: ibv_bind_mw(3)