User Manual

Memory Windows API cannot co-work with peer memory clients (PeerDirect).
Rev 2.2-1.0.1
Mellanox Technologies
141
4.23.1 Query Capabilities
Memory Windows are available if and only the hardware supports it. To verify whether Memory
Windows are available, run
ibv_exp_query_device.
For example:
truct ibv_exp_device_attr device_attr = {.comp_mask = IBV_EXP_DEVICE_ATTR_RESERVED -
1};
ibv_exp_query_device(context, & device_attr);
if (device_attr.exp_device_cap_flags & IBV_EXP_DEVICE_MEM_WINDOW ||
device_attr.exp_device_cap_flags & IBV_EXP_DEVICE_MW_TYPE_2B) {
/* Memory window is supported */
4.23.2 Allocating Memory Window
Allocating memory window is done by calling the ibv_alloc_mw verb.
type_mw = IBV_MW_TYPE_2/ IBV_MW_TYPE_1
mw = ibv_alloc_mw(pd, type_mw);
4.23.3 Binding Memory Windows
After allocated, memory window should be bound to a registered memory region. Memory
Region should have been registered using the
IBV_EXP_ACCESS_MW_BIND access flag.
• Binding Memory Window type 1 is done via the
ibv_exp_bind_mw verb.
struct ibv_ exp_ mw_bind mw_bind = { .comp_mask = IBV_EXP_BIND_MW_RESERVED - 1 };
ret = ibv_ exp_ bind_mw(qp, mw, &mw_bind);
• Binding memory window type 2B is done via the ibv_exp_post_send verb and a spe-
cific Work Request (WR) with
opcode = IBV_EXP_WR_BIND_MW
Prior to binding, please make sure to update the existing rkey.
ibv_inc_rkey(mw->rkey)
4.23.4 Invalidating Memory Window
Before rebinding Memory Window type 2, it must be invalidated using the ibv_exp_post_send
verb and a specific WR with opcode = IBV_EXP_WR_LOCAL_INV.
4.23.5 Deallocating Memory Window
Deallocating memory window is done using the ibv_dealloc_mw verb.
ibv_dealloc_mw(mw);