ibv_alloc_dm(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | Accessing an allocated device memory | Device memory registration | RETURN VALUE | NOTES | SEE ALSO | AUTHORS | COLOPHON

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

NAME         top

       ibv_alloc_dm, ibv_free_dm, ibv_memcpy_to/from_dm - allocate or
       free a device memory buffer (DMs) and perform memory copy to or
       from it

SYNOPSIS         top

       #include <infiniband/verbs.h>

       struct ibv_dm *ibv_alloc_dm(struct ibv_context *context,
                                   struct ibv_alloc_dm_attr *attr);

       int ibv_free_dm(struct ibv_dm *dm);

DESCRIPTION         top

       ibv_alloc_dm() allocates a device memory buffer for the RDMA
       device context context.  The argument attr is a pointer to an
       ibv_alloc_dm_attr struct, as defined in <infiniband/verbs.h>.

       ibv_free_dm() free the device memory buffer dm.

       struct ibv_alloc_dm_attr {
               size_t length;           /* Length of desired device memory buffer */
               uint32_t log_align_req;       /* Log base 2 of address alignment requirement */
               uint32_t comp_mask;      /* Compatibility mask that defines which of the following variables are valid */
       };

       Address alignment may be required in cases where RDMA atomic operations will be performed using the device memory.

       In such cases, the user may specify the device memory start address alignment using the log_align_req parameter

       in the allocation attributes struct.

Accessing an allocated device memory         top

       In order to perform a write/read memory access to an allocated device memory, a user could use the ibv_memcpy_to_dm
       and ibv_memcpy_from_dm calls respectively.

       int ibv_memcpy_to_dm(struct ibv_dm *dm, uint64_t dm_offset,
                            void *host_addr, size_t length);

       int ibv_memcpy_from_dm(void *host_addr, struct ibv_dm *dm,
                          uint64_t dm_offset, size_t length);

       dm_offest
       is the byte offset from the beginning of the allocated device memory buffer to access.

       host_addr
       is the host memory buffer address to access.

       length
       is the copy length in bytes.

Device memory registration         top

       User may register the allocated device memory as a memory region and use the lkey/rkey inside sge when posting receive
       or sending work request. This type of MR is defined as zero based and therefore any reference to it (specifically in sge)
       is done with a byte offset from the beginning of the region.

       This type of registration is done using ibv_reg_dm_mr.

       struct ibv_mr* ibv_reg_dm_mr(struct ibv_pd *pd, struct ibv_dm *dm, uint64_t dm_offset,
                         size_t length, uint32_t access);

       pd
       the associated pd for this registration.

       dm
       the associated dm for this registration.

       dm_offest
       is the byte offset from the beginning of the allocated device memory buffer to register.

       length
       the memory length to register.

       access
       mr access flags (Use enum ibv_access_flags). For this type of registration, user must set the IBV_ACCESS_ZERO_BASED
       flag.

RETURN VALUE         top

       ibv_alloc_dm() returns a pointer to an ibv_dm struct or NULL if
       the request fails.  The output dm contains the handle which could
       be used by user to import this device memory.

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

       ibv_reg_dm_mr() returns a pointer to an ibv_mr struct on success
       or NULL if request fails.

       ibv_memcpy_to_dm()/ibv_memcpy_from_dm() returns 0 on success or
       the failure reason value on failure.

NOTES         top

       ibv_alloc_dm() may fail if device has no more free device memory
       left, where the maximum amount of allocated memory is provided by
       the max_dm_size attribute in ibv_device_attr_ex struct.
       ibv_free_dm() may fail if any other resources (such as an MR) is
       still associated with the DM being freed.

SEE ALSO         top

       ibv_query_device_ex(3),

AUTHORS         top

       Ariel Levkovich <[email protected]>

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
       [email protected].  This page was obtained from the
       project's upstream Git repository
       ⟨https://github.com/linux-rdma/rdma-core.git⟩ on 2024-06-14.  (At
       that time, the date of the most recent commit that was found in
       the repository was 2024-06-10.)  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
       [email protected]

libibverbs                     2017-07-25                IBV_ALLOC_DM(3)