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NAME | SYNOPSIS | DESCRIPTION | Accessing an allocated device memory | Device memory registration | RETURN VALUE | NOTES | SEE ALSO | AUTHORS | COLOPHON |
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IBV_ALLOC_DM(3) Libibverbs Programmer's Manual IBV_ALLOC_DM(3)
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
#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);
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.
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.
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.
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.
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.
ibv_query_device_ex(3),
Ariel Levkovich <[email protected]>
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)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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