ibv_reg_mr(3) — Linux manual page


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

NAME         top

       ibv_reg_mr, ibv_reg_mr_iova, ibv_reg_dmabuf_mr, ibv_dereg_mr -
       register or deregister a memory region (MR)

SYNOPSIS         top

       #include <infiniband/verbs.h>

       struct ibv_mr *ibv_reg_mr(struct ibv_pd *pd, void *addr,
                                 size_t length, int access);

       struct ibv_mr *ibv_reg_mr_iova(struct ibv_pd *pd, void *addr,
                                      size_t length, uint64_t hca_va,
                                      int access);

       struct ibv_mr *ibv_reg_dmabuf_mr(struct ibv_pd *pd, uint64_t offset,
                                        size_t length, uint64_t iova,
                                        int fd, int access);

       int ibv_dereg_mr(struct ibv_mr *mr);

DESCRIPTION         top

       ibv_reg_mr() registers a memory region (MR) associated with the
       protection domain pd.  The MR's starting address is addr and its
       size is length.  The argument access describes the desired memory
       protection attributes; it is either 0 or the bitwise OR of one or
       more of the following flags:

              Enable Local Write Access

              Enable Remote Write Access

              Enable Remote Read Access

              Enable Remote Atomic Operation Access (if supported)

              Enable Remote Flush Operation with global visibility
              placement type (if supported)

              Enable Remote Flush Operation with persistence placement
              type (if supported)

              Enable Memory Window Binding

              Use byte offset from beginning of MR to access this MR,
              instead of a pointer address

              Create an on-demand paging MR

              Huge pages are guaranteed to be used for this MR,
              applicable with IBV_ACCESS_ON_DEMAND in explicit mode only

              This setting allows the NIC to relax the order that data
              is transfered between the network and the target memory
              region.  Relaxed ordering allows network initiated writes
              (such as incoming message send or RDMA write operations)
              to reach memory in an arbitrary order.  This can improve
              the performance of some applications.  However, relaxed
              ordering has the following impact: RDMA write-after-write
              message order is no longer guaranteed.  (Send messages
              will still match posted receive buffers in order.)  Back-
              to-back network writes that target the same memory region
              leave the region in an unknown state.  Relaxed ordering
              does not change completion semantics, such as data
              visibility.  That is, a completion still ensures that all
              data is visible, including data from prior transfers.
              Relaxed ordered operations will also not bypass atomic

       then IBV_ACCESS_LOCAL_WRITE must be set too.

       Local read access is always enabled for the MR.

       To create an implicit ODP MR, IBV_ACCESS_ON_DEMAND should be set,
       addr should be 0 and length should be SIZE_MAX.

       If IBV_ACCESS_HUGETLB is set, then application awares that for
       this MR all pages are huge and must promise it will never do
       anything to break huge pages.

       ibv_reg_mr_iova() ibv_reg_mr_iova is the same as the normal
       reg_mr, except that the user is allowed to specify the virtual
       base address of the MR when accessed through a lkey or rkey. The
       offset in the memory region is computed as 'addr + (iova -
       hca_va)'. Specifying 0 for hca_va has the same effect as

       ibv_reg_dmabuf_mr() registers a dma-buf based memory region (MR)
       associated with the protection domain pd.  The MR starts at
       offset of the dma-buf and its size is length.  The dma-buf is
       identified by the file descriptor fd.  The argument iova
       specifies the virtual base address of the MR when accessed
       through a lkey or rkey.  It must have the same page offset as
       offset.  The argument access describes the desired memory
       protection attributes; it is similar to the ibv_reg_mr case
       except that only the following flags are supported:

       ibv_dereg_mr() deregisters the MR mr.

RETURN VALUE         top

       ibv_reg_mr() / ibv_reg_mr_iova() / ibv_reg_dmabuf_mr() returns a
       pointer to the registered MR, or NULL if the request fails.  The
       local key (L_Key) field lkey is used as the lkey field of struct
       ibv_sge when posting buffers with ibv_post_* verbs, and the the
       remote key (R_Key) field rkey is used by remote processes to
       perform Atomic and RDMA operations.  The remote process places
       this rkey as the rkey field of struct ibv_send_wr passed to the
       ibv_post_send function.

       ibv_dereg_mr() 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

SEE ALSO         top

       ibv_alloc_pd(3), ibv_post_send(3), ibv_post_recv(3),

AUTHORS         top

       Dotan Barak <dotanba@gmail.com>

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 ⟨https://github.com/linux-rdma/rdma-core⟩.  If you have a bug
       report for this manual page, send it to
       linux-rdma@vger.kernel.org.  This page was obtained from the
       project's upstream Git repository
       ⟨https://github.com/linux-rdma/rdma-core.git⟩ on 2023-12-22.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2023-12-20.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

libibverbs                     2006-10-31                  IBV_REG_MR(3)

Pages that refer to this page: ibv_alloc_mw(3)ibv_alloc_pd(3)ibv_bind_mw(3)rdma_dereg_mr(3)rdma_post_recv(3)rdma_post_recvv(3)rdma_reg_msgs(3)rdma_reg_read(3)rdma_reg_write(3)