This is the new design of Memory Region (MR) for mlx PMD, in order to:
- Accommodate the new memory hotplug model.
- Support non-contiguous Mempool.
Signed-off-by: Yongseok Koh <ys...@mellanox.com>
---
 drivers/net/mlx5/mlx5.c          |   45 ++
 drivers/net/mlx5/mlx5.h          |   22 +
 drivers/net/mlx5/mlx5_defs.h     |    6 +
 drivers/net/mlx5/mlx5_ethdev.c   |   16 +
 drivers/net/mlx5/mlx5_mr.c       | 1194 ++++++++++++++++++++++++++++++++++++++
 drivers/net/mlx5/mlx5_mr.h       |  121 ++++
 drivers/net/mlx5/mlx5_rxq.c      |    8 +-
 drivers/net/mlx5/mlx5_rxtx.c     |    3 +
 drivers/net/mlx5/mlx5_rxtx.h     |   73 ++-
 drivers/net/mlx5/mlx5_rxtx_vec.h |    6 +-
 drivers/net/mlx5/mlx5_trigger.c  |   11 +
 drivers/net/mlx5/mlx5_txq.c      |   11 +
 12 files changed, 1508 insertions(+), 8 deletions(-)
 create mode 100644 drivers/net/mlx5/mlx5_mr.h

diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c
index 01d554758..2883f20af 100644
--- a/drivers/net/mlx5/mlx5.c
+++ b/drivers/net/mlx5/mlx5.c
@@ -41,6 +41,7 @@
 #include "mlx5_autoconf.h"
 #include "mlx5_defs.h"
 #include "mlx5_glue.h"
+#include "mlx5_mr.h"
 
 /* Device parameter to enable RX completion queue compression. */
 #define MLX5_RXQ_CQE_COMP_EN "rxq_cqe_comp_en"
@@ -84,10 +85,49 @@
 #define MLX5DV_CONTEXT_FLAGS_CQE_128B_COMP (1 << 4)
 #endif
 
+static const char *MZ_MLX5_PMD_SHARED_DATA = "mlx5_pmd_shared_data";
+
+/* Shared memory between primary and secondary processes. */
+struct mlx5_shared_data *mlx5_shared_data;
+
+/* Spinlock for mlx5_shared_data allocation. */
+static rte_spinlock_t mlx5_shared_data_lock = RTE_SPINLOCK_INITIALIZER;
+
 /** Driver-specific log messages type. */
 int mlx5_logtype;
 
 /**
+ * Prepare shared data between primary and secondary process.
+ */
+static void
+mlx5_prepare_shared_data(void)
+{
+       const struct rte_memzone *mz;
+
+       rte_spinlock_lock(&mlx5_shared_data_lock);
+       if (mlx5_shared_data == NULL) {
+               if (rte_eal_process_type() == RTE_PROC_PRIMARY) {
+                       /* Allocate shared memory. */
+                       mz = rte_memzone_reserve(MZ_MLX5_PMD_SHARED_DATA,
+                                                sizeof(*mlx5_shared_data),
+                                                SOCKET_ID_ANY, 0);
+               } else {
+                       /* Lookup allocated shared memory. */
+                       mz = rte_memzone_lookup(MZ_MLX5_PMD_SHARED_DATA);
+               }
+               if (mz == NULL)
+                       rte_panic("Cannot allocate mlx5 shared data\n");
+               mlx5_shared_data = mz->addr;
+               /* Initialize shared data. */
+               if (rte_eal_process_type() == RTE_PROC_PRIMARY) {
+                       LIST_INIT(&mlx5_shared_data->mem_event_cb_list);
+                       rte_rwlock_init(&mlx5_shared_data->mem_event_rwlock);
+               }
+       }
+       rte_spinlock_unlock(&mlx5_shared_data_lock);
+}
+
+/**
  * Retrieve integer value from environment variable.
  *
  * @param[in] name
@@ -201,6 +241,7 @@ mlx5_dev_close(struct rte_eth_dev *dev)
                priv->txqs = NULL;
        }
        mlx5_flow_delete_drop_queue(dev);
+       mlx5_mr_release(dev);
        if (priv->pd != NULL) {
                assert(priv->ctx != NULL);
                claim_zero(mlx5_glue->dealloc_pd(priv->pd));
@@ -633,6 +674,8 @@ mlx5_pci_probe(struct rte_pci_driver *pci_drv __rte_unused,
        struct ibv_counter_set_description cs_desc;
 #endif
 
+       /* Prepare shared data between primary and secondary process. */
+       mlx5_prepare_shared_data();
        assert(pci_drv == &mlx5_driver);
        /* Get mlx5_dev[] index. */
        idx = mlx5_dev_idx(&pci_dev->addr);
@@ -1293,6 +1336,8 @@ rte_mlx5_pmd_init(void)
        }
        mlx5_glue->fork_init();
        rte_pci_register(&mlx5_driver);
+       rte_mem_event_callback_register("MLX5_MEM_EVENT_CB",
+                                       mlx5_mr_mem_event_cb);
 }
 
 RTE_PMD_EXPORT_NAME(net_mlx5, __COUNTER__);
diff --git a/drivers/net/mlx5/mlx5.h b/drivers/net/mlx5/mlx5.h
index 47d266c90..d3fc74dc1 100644
--- a/drivers/net/mlx5/mlx5.h
+++ b/drivers/net/mlx5/mlx5.h
@@ -26,11 +26,13 @@
 #include <rte_pci.h>
 #include <rte_ether.h>
 #include <rte_ethdev_driver.h>
+#include <rte_rwlock.h>
 #include <rte_interrupts.h>
 #include <rte_errno.h>
 #include <rte_flow.h>
 
 #include "mlx5_utils.h"
+#include "mlx5_mr.h"
 #include "mlx5_rxtx.h"
 #include "mlx5_autoconf.h"
 #include "mlx5_defs.h"
@@ -50,6 +52,16 @@ enum {
        PCI_DEVICE_ID_MELLANOX_CONNECTX5EXVF = 0x101a,
 };
 
+LIST_HEAD(mlx5_dev_list, priv);
+
+/* Shared memory between primary and secondary processes. */
+struct mlx5_shared_data {
+       struct mlx5_dev_list mem_event_cb_list;
+       rte_rwlock_t mem_event_rwlock;
+};
+
+extern struct mlx5_shared_data *mlx5_shared_data;
+
 struct mlx5_xstats_ctrl {
        /* Number of device stats. */
        uint16_t stats_n;
@@ -119,7 +131,10 @@ struct mlx5_verbs_alloc_ctx {
        const void *obj; /* Pointer to the DPDK object. */
 };
 
+LIST_HEAD(mlx5_mr_list, mlx5_mr);
+
 struct priv {
+       LIST_ENTRY(priv) mem_event_cb; /* Called by memory event callback. */
        struct rte_eth_dev_data *dev_data;  /* Pointer to device data. */
        struct ibv_context *ctx; /* Verbs context. */
        struct ibv_device_attr_ex device_attr; /* Device properties. */
@@ -146,6 +161,13 @@ struct priv {
        struct mlx5_hrxq_drop *flow_drop_queue; /* Flow drop queue. */
        struct mlx5_flows flows; /* RTE Flow rules. */
        struct mlx5_flows ctrl_flows; /* Control flow rules. */
+       struct {
+               uint32_t dev_gen; /* Generation number to flush local caches. */
+               rte_rwlock_t rwlock; /* MR Lock. */
+               struct mlx5_mr_btree cache; /* Global MR cache table. */
+               struct mlx5_mr_list mr_list; /* Registered MR list. */
+               struct mlx5_mr_list mr_free_list; /* Freed MR list. */
+       } mr;
        LIST_HEAD(rxq, mlx5_rxq_ctrl) rxqsctrl; /* DPDK Rx queues. */
        LIST_HEAD(rxqibv, mlx5_rxq_ibv) rxqsibv; /* Verbs Rx queues. */
        LIST_HEAD(hrxq, mlx5_hrxq) hrxqs; /* Verbs Hash Rx queues. */
diff --git a/drivers/net/mlx5/mlx5_defs.h b/drivers/net/mlx5/mlx5_defs.h
index f9093777d..72e80af26 100644
--- a/drivers/net/mlx5/mlx5_defs.h
+++ b/drivers/net/mlx5/mlx5_defs.h
@@ -37,6 +37,12 @@
  */
 #define MLX5_TX_COMP_THRESH_INLINE_DIV (1 << 3)
 
+/* Size of per-queue MR cache array for linear search. */
+#define MLX5_MR_CACHE_N 8
+
+/* Size of MR cache table for binary search. */
+#define MLX5_MR_BTREE_CACHE_N 256
+
 /*
  * If defined, only use software counters. The PMD will never ask the hardware
  * for these, and many of them won't be available.
diff --git a/drivers/net/mlx5/mlx5_ethdev.c b/drivers/net/mlx5/mlx5_ethdev.c
index 746b94f73..6bb43cf4e 100644
--- a/drivers/net/mlx5/mlx5_ethdev.c
+++ b/drivers/net/mlx5/mlx5_ethdev.c
@@ -34,6 +34,7 @@
 #include <rte_interrupts.h>
 #include <rte_malloc.h>
 #include <rte_string_fns.h>
+#include <rte_rwlock.h>
 
 #include "mlx5.h"
 #include "mlx5_glue.h"
@@ -413,6 +414,21 @@ mlx5_dev_configure(struct rte_eth_dev *dev)
                if (++j == rxqs_n)
                        j = 0;
        }
+       /*
+        * Once the device is added to the list of memory event callback, its
+        * global MR cache table cannot be expanded on the fly because of
+        * deadlock. If it overflows, lookup should be done by searching MR list
+        * linearly, which is slow.
+        */
+       if (mlx5_mr_btree_init(&priv->mr.cache, MLX5_MR_BTREE_CACHE_N * 2,
+                              dev->device->numa_node)) {
+               /* rte_errno is already set. */
+               return -rte_errno;
+       }
+       rte_rwlock_write_lock(&mlx5_shared_data->mem_event_rwlock);
+       LIST_INSERT_HEAD(&mlx5_shared_data->mem_event_cb_list,
+                        priv, mem_event_cb);
+       rte_rwlock_write_unlock(&mlx5_shared_data->mem_event_rwlock);
        return 0;
 }
 
diff --git a/drivers/net/mlx5/mlx5_mr.c b/drivers/net/mlx5/mlx5_mr.c
index 736c40ae4..e964912bb 100644
--- a/drivers/net/mlx5/mlx5_mr.c
+++ b/drivers/net/mlx5/mlx5_mr.c
@@ -13,8 +13,1202 @@
 
 #include <rte_mempool.h>
 #include <rte_malloc.h>
+#include <rte_rwlock.h>
 
 #include "mlx5.h"
+#include "mlx5_mr.h"
 #include "mlx5_rxtx.h"
 #include "mlx5_glue.h"
 
+struct mr_find_contig_memsegs_data {
+       uintptr_t addr;
+       uintptr_t start;
+       uintptr_t end;
+       const struct rte_memseg_list *msl;
+};
+
+struct mr_update_mp_data {
+       struct rte_eth_dev *dev;
+       struct mlx5_mr_ctrl *mr_ctrl;
+       int ret;
+};
+
+/**
+ * Expand B-tree table to a given size. Can't be called with holding
+ * memory_hotplug_lock or priv->mr.rwlock due to rte_realloc().
+ *
+ * @param bt
+ *   Pointer to B-tree structure.
+ * @param n
+ *   Number of entries for expansion.
+ *
+ * @return
+ *   0 on success, -1 on failure.
+ */
+static int
+mr_btree_expand(struct mlx5_mr_btree *bt, int n)
+{
+       void *mem;
+       int ret = 0;
+
+       if (n <= bt->size)
+               return ret;
+       /*
+        * Downside of directly using rte_realloc() is that SOCKET_ID_ANY is
+        * used inside if there's no room to expand. Because this is a quite
+        * rare case and a part of very slow path, it is very acceptable.
+        * Initially cache_bh[] will be given practically enough space and once
+        * it is expanded, expansion wouldn't be needed again ever.
+        */
+       mem = rte_realloc(bt->table, n * sizeof(struct mlx5_mr_cache), 0);
+       if (mem == NULL) {
+               /* Not an error, B-tree search will be skipped. */
+               DRV_LOG(WARNING, "failed to expand MR B-tree (%p) table",
+                       (void *)bt);
+               ret = -1;
+       } else {
+               DRV_LOG(DEBUG, "expanded MR B-tree table (size=%u)", n);
+               bt->table = mem;
+               bt->size = n;
+       }
+       return ret;
+}
+
+/**
+ * Look up LKey from given B-tree lookup table, store the last index and return
+ * searched LKey.
+ *
+ * @param bt
+ *   Pointer to B-tree structure.
+ * @param[out] idx
+ *   Pointer to index. Even on searh failure, returns index where it stops
+ *   searching so that index can be used when inserting a new entry.
+ * @param addr
+ *   Search key.
+ *
+ * @return
+ *   Searched LKey on success, UINT32_MAX on no match.
+ */
+static uint32_t
+mr_btree_lookup(struct mlx5_mr_btree *bt, uint16_t *idx, uintptr_t addr)
+{
+       struct mlx5_mr_cache *lkp_tbl;
+       uint16_t n;
+       uint16_t base = 0;
+
+       assert(bt != NULL);
+       lkp_tbl = *bt->table;
+       n = bt->len;
+       /* First entry must be NULL for comparison. */
+       assert(bt->len > 0 || (lkp_tbl[0].start == 0 &&
+                              lkp_tbl[0].lkey == UINT32_MAX));
+       /* Binary search. */
+       do {
+               register uint16_t delta = n >> 1;
+
+               if (addr < lkp_tbl[base + delta].start) {
+                       n = delta;
+               } else {
+                       base += delta;
+                       n -= delta;
+               }
+       } while (n > 1);
+       assert(addr >= lkp_tbl[base].start);
+       *idx = base;
+       if (addr < lkp_tbl[base].end)
+               return lkp_tbl[base].lkey;
+       /* Not found. */
+       return UINT32_MAX;
+}
+
+/**
+ * Insert an entry to B-tree lookup table.
+ *
+ * @param bt
+ *   Pointer to B-tree structure.
+ * @param entry
+ *   Pointer to new entry to insert.
+ *
+ * @return
+ *   0 on success, -1 on failure.
+ */
+static int
+mr_btree_insert(struct mlx5_mr_btree *bt, struct mlx5_mr_cache *entry)
+{
+       struct mlx5_mr_cache *lkp_tbl;
+       uint16_t idx = 0;
+       size_t shift;
+
+       assert(bt != NULL);
+       assert(bt->len <= bt->size);
+       assert(bt->len > 0);
+       lkp_tbl = *bt->table;
+       /* Find out the slot for insertion. */
+       if (mr_btree_lookup(bt, &idx, entry->start) != UINT32_MAX) {
+               DRV_LOG(DEBUG,
+                       "abort insertion to B-tree(%p):"
+                       " already exist at idx=%u [0x%lx, 0x%lx) lkey=0x%x",
+                       (void *)bt, idx, entry->start, entry->end, entry->lkey);
+               /* Already exist, return. */
+               return 0;
+       }
+       /* If table is full, return error. */
+       if (unlikely(bt->len == bt->size)) {
+               bt->overflow = 1;
+               return -1;
+       }
+       /* Insert entry. */
+       ++idx;
+       shift = (bt->len - idx) * sizeof(struct mlx5_mr_cache);
+       if (shift)
+               memmove(&lkp_tbl[idx + 1], &lkp_tbl[idx], shift);
+       lkp_tbl[idx] = *entry;
+       bt->len++;
+       DRV_LOG(DEBUG,
+               "inserted B-tree(%p)[%u], [0x%lx, 0x%lx) lkey=0x%x",
+               (void *)bt, idx, entry->start, entry->end, entry->lkey);
+       return 0;
+}
+
+/**
+ * Initialize B-tree and allocate memory for lookup table.
+ *
+ * @param bt
+ *   Pointer to B-tree structure.
+ * @param n
+ *   Number of entries to allocate.
+ * @param socket
+ *   NUMA socket on which memory must be allocated.
+ *
+ * @return
+ *   0 on success, a negative errno value otherwise and rte_errno is set.
+ */
+int
+mlx5_mr_btree_init(struct mlx5_mr_btree *bt, int n, int socket)
+{
+       if (bt == NULL) {
+               rte_errno = EINVAL;
+               return -rte_errno;
+       }
+       memset(bt, 0, sizeof(*bt));
+       bt->table = rte_calloc_socket("B-tree table",
+                                     n, sizeof(struct mlx5_mr_cache),
+                                     0, socket);
+       if (bt->table == NULL) {
+               rte_errno = ENOMEM;
+               DRV_LOG(ERR,
+                       "failed to allocate memory for btree cache on socket 
%d",
+                       socket);
+               return -rte_errno;
+       }
+       bt->size = n;
+       /* First entry must be NULL for binary search. */
+       (*bt->table)[bt->len++] = (struct mlx5_mr_cache) {
+               .lkey = UINT32_MAX,
+       };
+       DRV_LOG(DEBUG, "initialized B-tree %p with table %p",
+               (void *)bt, (void *)bt->table);
+       return 0;
+}
+
+/**
+ * Free B-tree resources.
+ *
+ * @param bt
+ *   Pointer to B-tree structure.
+ */
+void
+mlx5_mr_btree_free(struct mlx5_mr_btree *bt)
+{
+       if (bt == NULL)
+               return;
+       DRV_LOG(DEBUG, "freeing B-tree %p with table %p",
+               (void *)bt, (void *)bt->table);
+       rte_free(bt->table);
+       memset(bt, 0, sizeof(*bt));
+}
+
+/**
+ * Dump all the entries in a B-tree
+ *
+ * @param bt
+ *   Pointer to B-tree structure.
+ */
+static void
+mlx5_mr_btree_dump(struct mlx5_mr_btree *bt)
+{
+       int idx;
+       struct mlx5_mr_cache *lkp_tbl;
+
+       if (bt == NULL)
+               return;
+       lkp_tbl = *bt->table;
+       for (idx = 0; idx < bt->len; ++idx) {
+               struct mlx5_mr_cache *entry = &lkp_tbl[idx];
+
+               DRV_LOG(DEBUG,
+                       "B-tree(%p)[%u], [0x%lx, 0x%lx) lkey=0x%x",
+                       (void *)bt, idx, entry->start, entry->end, entry->lkey);
+       }
+}
+
+/**
+ * Find virtually contiguous memory chunk in a given MR.
+ *
+ * @param dev
+ *   Pointer to MR structure.
+ * @param[out] entry
+ *   Pointer to returning MR cache entry. If not found, this will not be
+ *   updated.
+ * @param start_idx
+ *   Start index of the memseg bitmap.
+ *
+ * @return
+ *   Next index to go on lookup.
+ */
+static int
+mr_find_next_chunk(struct mlx5_mr *mr, struct mlx5_mr_cache *entry,
+                  int base_idx)
+{
+       uintptr_t start = 0;
+       uintptr_t end = 0;
+       uint32_t idx = 0;
+
+       for (idx = base_idx; idx < mr->ms_bmp_n; ++idx) {
+               if (rte_bitmap_get(mr->ms_bmp, idx)) {
+                       const struct rte_memseg_list *msl;
+                       const struct rte_memseg *ms;
+
+                       msl = mr->msl;
+                       ms = rte_fbarray_get(&msl->memseg_arr,
+                                            mr->ms_base_idx + idx);
+                       assert(msl->page_sz == ms->hugepage_sz);
+                       if (!start)
+                               start = ms->addr_64;
+                       end = ms->addr_64 + ms->hugepage_sz;
+               } else if (start) {
+                       /* Passed the end of a fragment. */
+                       break;
+               }
+       }
+       if (start) {
+               /* Found one chunk. */
+               entry->start = start;
+               entry->end = end;
+               entry->lkey = rte_cpu_to_be_32(mr->ibv_mr->lkey);
+       }
+       return idx;
+}
+
+/**
+ * Insert a MR to the global B-tree cache. It may fail due to low-on-memory.
+ * Then, this entry will have to be searched by mr_lookup_dev_list() in
+ * mlx5_mr_create() on miss.
+ *
+ * @param dev
+ *   Pointer to Ethernet device.
+ * @param mr
+ *   Pointer to MR to insert.
+ *
+ * @return
+ *   0 on success, -1 on failure.
+ */
+static int
+mr_insert_dev_cache(struct rte_eth_dev *dev, struct mlx5_mr *mr)
+{
+       struct priv *priv = dev->data->dev_private;
+       unsigned int n;
+
+       DRV_LOG(DEBUG, "port %u inserting MR(%p) to global cache",
+               dev->data->port_id, (void *)mr);
+       for (n = 0; n < mr->ms_bmp_n; ) {
+               struct mlx5_mr_cache entry = { 0, };
+
+               /* Find a contiguous chunk and advance the index. */
+               n = mr_find_next_chunk(mr, &entry, n);
+               if (!entry.end)
+                       break;
+               if (mr_btree_insert(&priv->mr.cache, &entry) < 0) {
+                       /*
+                        * Overflowed, but the global table cannot be expanded
+                        * because of deadlock.
+                        */
+                       return -1;
+               }
+       }
+       return 0;
+}
+
+/**
+ * Look up address in the original global MR list.
+ *
+ * @param dev
+ *   Pointer to Ethernet device.
+ * @param[out] entry
+ *   Pointer to returning MR cache entry. If no match, this will not be 
updated.
+ * @param addr
+ *   Search key.
+ *
+ * @return
+ *   Found MR on match, NULL otherwise.
+ */
+static struct mlx5_mr *
+mr_lookup_dev_list(struct rte_eth_dev *dev, struct mlx5_mr_cache *entry,
+                  uintptr_t addr)
+{
+       struct priv *priv = dev->data->dev_private;
+       struct mlx5_mr *mr;
+
+       /* Iterate all the existing MRs. */
+       LIST_FOREACH(mr, &priv->mr.mr_list, mr) {
+               unsigned int n;
+
+               if (mr->ms_n == 0)
+                       continue;
+               for (n = 0; n < mr->ms_bmp_n; ) {
+                       struct mlx5_mr_cache ret = { 0, };
+
+                       n = mr_find_next_chunk(mr, &ret, n);
+                       if (addr >= ret.start && addr < ret.end) {
+                               /* Found. */
+                               *entry = ret;
+                               return mr;
+                       }
+               }
+       }
+       return NULL;
+}
+
+/**
+ * Look up address on device.
+ *
+ * @param dev
+ *   Pointer to Ethernet device.
+ * @param[out] entry
+ *   Pointer to returning MR cache entry. If no match, this will not be 
updated.
+ * @param addr
+ *   Search key.
+ *
+ * @return
+ *   Searched LKey on success, UINT32_MAX on failure and rte_errno is set.
+ */
+static uint32_t
+mr_lookup_dev(struct rte_eth_dev *dev, struct mlx5_mr_cache *entry,
+             uintptr_t addr)
+{
+       struct priv *priv = dev->data->dev_private;
+       uint16_t idx;
+       uint32_t lkey = UINT32_MAX;
+       struct mlx5_mr *mr;
+
+       /*
+        * If the global cache has overflowed since it failed to expand the
+        * B-tree table, it can't have all the exisitng MRs. Then, the address
+        * has to be searched by traversing the original MR list instead, which
+        * is very slow path. Otherwise, the global cache is all inclusive.
+        */
+       if (!unlikely(priv->mr.cache.overflow)) {
+               lkey = mr_btree_lookup(&priv->mr.cache, &idx, addr);
+               if (lkey != UINT32_MAX)
+                       *entry = (*priv->mr.cache.table)[idx];
+       } else {
+               /* Falling back to the slowest path. */
+               mr = mr_lookup_dev_list(dev, entry, addr);
+               if (mr != NULL)
+                       lkey = entry->lkey;
+       }
+       assert(lkey == UINT32_MAX || (addr >= entry->start &&
+                                     addr < entry->end));
+       return lkey;
+}
+
+/**
+ * Free MR resources. MR lock must not be held to avoid a deadlock. rte_free()
+ * can raise memory free event and the callback function will spin on the lock.
+ *
+ * @param mr
+ *   Pointer to MR to free.
+ */
+static void
+mr_free(struct mlx5_mr *mr)
+{
+       if (mr == NULL)
+               return;
+       DRV_LOG(DEBUG, "freeing MR(%p):", (void *)mr);
+       if (mr->ibv_mr != NULL)
+               claim_zero(mlx5_glue->dereg_mr(mr->ibv_mr));
+       if (mr->ms_bmp != NULL)
+               rte_bitmap_free(mr->ms_bmp);
+       rte_free(mr);
+}
+
+/**
+ * Free Memory Region (MR).
+ *
+ * @param dev
+ *   Pointer to Ethernet device.
+ * @param mr
+ *   Pointer to MR to free.
+ */
+void
+mlx5_mr_free(struct rte_eth_dev *dev, struct mlx5_mr *mr)
+{
+       struct priv *priv = dev->data->dev_private;
+
+       /* Detach from the list and free resources later. */
+       rte_rwlock_write_lock(&priv->mr.rwlock);
+       LIST_REMOVE(mr, mr);
+       rte_rwlock_write_unlock(&priv->mr.rwlock);
+       /*
+        * rte_free() inside can't be called with holding the lock. This could
+        * cause deadlock when calling free callback.
+        */
+       mr_free(mr);
+       DRV_LOG(DEBUG, "port %u MR(%p) freed", dev->data->port_id, (void *)mr);
+}
+
+/**
+ * Releass resources of detached MR having no online entry.
+ *
+ * @param dev
+ *   Pointer to Ethernet device.
+ */
+static void
+mlx5_mr_garbage_collect(struct rte_eth_dev *dev)
+{
+       struct priv *priv = dev->data->dev_private;
+       struct mlx5_mr *mr_next;
+       struct mlx5_mr_list free_list = LIST_HEAD_INITIALIZER(free_list);
+
+       /* Must be called from the primary process. */
+       assert(rte_eal_process_type() == RTE_PROC_PRIMARY);
+       /*
+        * MR can't be freed with holding the lock because rte_free() could call
+        * memory free callback function. This will be a deadlock situation.
+        */
+       rte_rwlock_write_lock(&priv->mr.rwlock);
+       /* Detach the whole free list and release it after unlocking. */
+       free_list = priv->mr.mr_free_list;
+       LIST_INIT(&priv->mr.mr_free_list);
+       rte_rwlock_write_unlock(&priv->mr.rwlock);
+       /* Release resources. */
+       mr_next = LIST_FIRST(&free_list);
+       while (mr_next != NULL) {
+               struct mlx5_mr *mr = mr_next;
+
+               mr_next = LIST_NEXT(mr, mr);
+               mr_free(mr);
+       }
+}
+
+/* Called during rte_memseg_contig_walk() by mlx5_mr_create(). */
+static int
+mr_find_contig_memsegs_cb(const struct rte_memseg_list *msl,
+                         const struct rte_memseg *ms, size_t len, void *arg)
+{
+       struct mr_find_contig_memsegs_data *data = arg;
+
+       if (data->addr < ms->addr_64 || data->addr >= ms->addr_64 + len)
+               return 0;
+       /* Found, save it and stop walking. */
+       data->start = ms->addr_64;
+       data->end = ms->addr_64 + len;
+       data->msl = msl;
+       return 1;
+}
+
+/**
+ * Create a new global Memroy Region (MR) for a missing virtual address.
+ * Register entire virtually contiguous memory chunk around the address.
+ *
+ * @param dev
+ *   Pointer to Ethernet device.
+ * @param[out] entry
+ *   Pointer to returning MR cache entry, found in the global cache or newly
+ *   created. If failed to create one, this will not be updated.
+ * @param addr
+ *   Target virtual address to register.
+ *
+ * @return
+ *   Searched LKey on success, UINT32_MAX on failure and rte_errno is set.
+ */
+static uint32_t
+mlx5_mr_create(struct rte_eth_dev *dev, struct mlx5_mr_cache *entry,
+              uintptr_t addr)
+{
+       struct priv *priv = dev->data->dev_private;
+       struct rte_mem_config *mcfg = rte_eal_get_configuration()->mem_config;
+       const struct rte_memseg_list *msl;
+       const struct rte_memseg *ms;
+       struct mlx5_mr *mr = NULL;
+       size_t len;
+       uint32_t ms_n;
+       uint32_t bmp_size;
+       void *bmp_mem;
+       int ms_idx_shift = -1;
+       unsigned int n;
+       struct mr_find_contig_memsegs_data data = {
+               .addr = addr,
+       };
+       struct mr_find_contig_memsegs_data data_re;
+
+       DRV_LOG(DEBUG, "port %u creating a MR using address (%p)",
+               dev->data->port_id, (void *)addr);
+       if (rte_eal_process_type() != RTE_PROC_PRIMARY) {
+               DRV_LOG(WARNING,
+                       "port %u using address (%p) of unregistered mempool"
+                       " in secondary process, please create mempool"
+                       " before rte_eth_dev_start()",
+                       dev->data->port_id, (void *)addr);
+               rte_errno = EPERM;
+               goto err_nolock;
+       }
+       /*
+        * Release detached MRs if any. This can't be called with holding either
+        * memory_hotplug_lock or priv->mr.rwlock. MRs on the free list have
+        * been detached by the memory free event but it couldn't be released
+        * inside the callback due to deadlock. As a result, releasing resources
+        * is quite opportunistic.
+        */
+       mlx5_mr_garbage_collect(dev);
+       /*
+        * Find out a contiguous virtual address chunk in use, to which the
+        * given address belongs, in order to register maximum range. In the
+        * best case where mempools are not dynamically recreated and
+        * '--socket-mem' is speicified as an EAL option, it is very likely to
+        * have only one MR(LKey) per a socket and per a hugepage-size even
+        * though the system memory is highly fragmented.
+        */
+       if (!rte_memseg_contig_walk(mr_find_contig_memsegs_cb, &data)) {
+               DRV_LOG(WARNING,
+                       "port %u unable to find virtually contigous"
+                       " chunk for address (%p)."
+                       " rte_memseg_contig_walk() failed.",
+                       dev->data->port_id, (void *)addr);
+               rte_errno = ENXIO;
+               goto err_nolock;
+       }
+alloc_resources:
+       /* Addresses must be page-aligned. */
+       assert(rte_is_aligned((void *)data.start, data.msl->page_sz));
+       assert(rte_is_aligned((void *)data.end, data.msl->page_sz));
+       msl = data.msl;
+       ms = rte_mem_virt2memseg((void *)data.start, msl);
+       len = data.end - data.start;
+       assert(msl->page_sz == ms->hugepage_sz);
+       /* Number of memsegs in the range. */
+       ms_n = len / msl->page_sz;
+       DRV_LOG(DEBUG,
+               "port %u extending %p to [0x%lx, 0x%lx), page_sz=0x%lx, 
ms_n=%u",
+               dev->data->port_id, (void *)addr,
+               data.start, data.end, msl->page_sz, ms_n);
+       /* Size of memory for bitmap. */
+       bmp_size = rte_bitmap_get_memory_footprint(ms_n);
+       mr = rte_zmalloc_socket(NULL,
+                               RTE_ALIGN_CEIL(sizeof(*mr),
+                                              RTE_CACHE_LINE_SIZE) +
+                               bmp_size,
+                               RTE_CACHE_LINE_SIZE, msl->socket_id);
+       if (mr == NULL) {
+               DRV_LOG(WARNING,
+                       "port %u unable to allocate memory for a new MR of"
+                       " address (%p).",
+                       dev->data->port_id, (void *)addr);
+               rte_errno = ENOMEM;
+               goto err_nolock;
+       }
+       mr->msl = msl;
+       /*
+        * Save the index of the first memseg and initialize memseg bitmap. To
+        * see if a memseg of ms_idx in the memseg-list is still valid, check:
+        *      rte_bitmap_get(mr->bmp, ms_idx - mr->ms_base_idx)
+        */
+       mr->ms_base_idx = rte_fbarray_find_idx(&msl->memseg_arr, ms);
+       bmp_mem = RTE_PTR_ALIGN_CEIL(mr + 1, RTE_CACHE_LINE_SIZE);
+       mr->ms_bmp = rte_bitmap_init(ms_n, bmp_mem, bmp_size);
+       if (mr->ms_bmp == NULL) {
+               DRV_LOG(WARNING,
+                       "port %u unable to initialize bitamp for a new MR of"
+                       " address (%p).",
+                       dev->data->port_id, (void *)addr);
+               rte_errno = EINVAL;
+               goto err_nolock;
+       }
+       /*
+        * Should recheck whether the extended contiguous chunk is still valid.
+        * Because memory_hotplug_lock can't be held if there's any memory
+        * related calls in a critical path, resource allocation above can't be
+        * locked. If the memory has been changed at this point, try again with
+        * just single page. If not, go on with the big chunk atomically from
+        * here.
+        */
+       rte_rwlock_read_lock(&mcfg->memory_hotplug_lock);
+       data_re = data;
+       if (len > msl->page_sz &&
+           !rte_memseg_contig_walk(mr_find_contig_memsegs_cb, &data_re)) {
+               DRV_LOG(WARNING,
+                       "port %u unable to find virtually contigous"
+                       " chunk for address (%p)."
+                       " rte_memseg_contig_walk() failed.",
+                       dev->data->port_id, (void *)addr);
+               rte_errno = ENXIO;
+               goto err_memlock;
+       }
+       if (data.start != data_re.start || data.end != data_re.end) {
+               /*
+                * The extended contiguous chunk has been changed. Try again
+                * with single memseg instead.
+                */
+               data.start = RTE_ALIGN_FLOOR(addr, msl->page_sz);
+               data.end = data.start + msl->page_sz;
+               rte_rwlock_read_unlock(&mcfg->memory_hotplug_lock);
+               mr_free(mr);
+               goto alloc_resources;
+       }
+       assert(data.msl == data_re.msl);
+       rte_rwlock_write_lock(&priv->mr.rwlock);
+       /*
+        * Check the address is really missing. If other thread already created
+        * one or it is not found due to overflow, abort and return.
+        */
+       if (mr_lookup_dev(dev, entry, addr) != UINT32_MAX) {
+               /*
+                * Insert to the global cache table. It may fail due to
+                * low-on-memory. Then, this entry will have to be searched
+                * here again.
+                */
+               mr_btree_insert(&priv->mr.cache, entry);
+               DRV_LOG(DEBUG,
+                       "port %u found MR for %p on final lookup, abort",
+                       dev->data->port_id, (void *)addr);
+               rte_rwlock_write_unlock(&priv->mr.rwlock);
+               rte_rwlock_read_unlock(&mcfg->memory_hotplug_lock);
+               /*
+                * Must be unlocked before calling rte_free() because
+                * mlx5_mr_mem_event_free_cb() can be called inside.
+                */
+               mr_free(mr);
+               return entry->lkey;
+       }
+       /*
+        * Trim start and end addresses for verbs MR. Set bits for registering
+        * memsegs but exclude already registered ones. Bitmap can be
+        * fragmented.
+        */
+       for (n = 0; n < ms_n; ++n) {
+               uintptr_t start;
+               struct mlx5_mr_cache ret = { 0, };
+
+               start = data_re.start + n * msl->page_sz;
+               /* Exclude memsegs already registered by other MRs. */
+               if (mr_lookup_dev(dev, &ret, start) == UINT32_MAX) {
+                       /*
+                        * Start from the first unregistered memseg in the
+                        * extended range.
+                        */
+                       if (ms_idx_shift == -1) {
+                               mr->ms_base_idx += n;
+                               data.start = start;
+                               ms_idx_shift = n;
+                       }
+                       data.end = start + msl->page_sz;
+                       rte_bitmap_set(mr->ms_bmp, n - ms_idx_shift);
+                       ++mr->ms_n;
+               }
+       }
+       len = data.end - data.start;
+       mr->ms_bmp_n = len / msl->page_sz;
+       assert(ms_idx_shift + mr->ms_bmp_n <= ms_n);
+       /*
+        * Finally create a verbs MR for the memory chunk. ibv_reg_mr() can be
+        * called with holding the memory lock because it doesn't use
+        * mlx5_alloc_buf_extern() which eventually calls rte_malloc_socket()
+        * through mlx5_alloc_verbs_buf().
+        */
+       mr->ibv_mr = mlx5_glue->reg_mr(priv->pd, (void *)data.start, len,
+                                      IBV_ACCESS_LOCAL_WRITE);
+       if (mr->ibv_mr == NULL) {
+               DRV_LOG(WARNING,
+                       "port %u fail to create a verbs MR for address (%p)",
+                       dev->data->port_id, (void *)addr);
+               rte_errno = EINVAL;
+               goto err_mrlock;
+       }
+       assert((uintptr_t)mr->ibv_mr->addr == data.start);
+       assert(mr->ibv_mr->length == len);
+       LIST_INSERT_HEAD(&priv->mr.mr_list, mr, mr);
+       DRV_LOG(DEBUG,
+               "port %u MR CREATED (%p) for %p:\n"
+               "  [0x%lx, 0x%lx), lkey=0x%x base_idx=%u ms_n=%u, ms_bmp_n=%u",
+               dev->data->port_id, (void *)mr, (void *)addr,
+               data.start, data.end, rte_cpu_to_be_32(mr->ibv_mr->lkey),
+               mr->ms_base_idx, mr->ms_n, mr->ms_bmp_n);
+       /* Insert to the global cache table. */
+       mr_insert_dev_cache(dev, mr);
+       /* Fill in output data. */
+       mr_lookup_dev(dev, entry, addr);
+       /* Lookup can't fail. */
+       assert(entry->lkey != UINT32_MAX);
+       rte_rwlock_write_unlock(&priv->mr.rwlock);
+       rte_rwlock_read_unlock(&mcfg->memory_hotplug_lock);
+       return entry->lkey;
+err_mrlock:
+       rte_rwlock_write_unlock(&priv->mr.rwlock);
+err_memlock:
+       rte_rwlock_read_unlock(&mcfg->memory_hotplug_lock);
+err_nolock:
+       /*
+        * In case of error, as this can be called in a datapath, a warning
+        * message per an error is preferable instead. Must be unlocked before
+        * calling rte_free() because mlx5_mr_mem_event_free_cb() can be called
+        * inside.
+        */
+       mr_free(mr);
+       return UINT32_MAX;
+}
+
+/**
+ * Rebuild the global B-tree cache of device from the original MR list.
+ *
+ * @param dev
+ *   Pointer to Ethernet device.
+ */
+static void
+mr_rebuild_dev_cache(struct rte_eth_dev *dev)
+{
+       struct priv *priv = dev->data->dev_private;
+       struct mlx5_mr *mr;
+
+       DRV_LOG(DEBUG, "port %u rebuild dev cache[]", dev->data->port_id);
+       /* Flush cache to rebuild. */
+       priv->mr.cache.len = 1;
+       priv->mr.cache.overflow = 0;
+       /* Iterate all the existing MRs. */
+       LIST_FOREACH(mr, &priv->mr.mr_list, mr)
+               if (mr_insert_dev_cache(dev, mr) < 0)
+                       return;
+}
+
+/**
+ * Callback for memory free event. Iterate freed memsegs and check whether it
+ * belongs to an existing MR. If found, clear the bit from bitmap of MR. As a
+ * result, the MR would be fragmented. If it becomes empty, the MR will be 
freed
+ * later by mlx5_mr_garbage_collect(). Even if this callback is called from a
+ * secondary process, the garbage collector will be called in primary process
+ * as the secondary process can't call mlx5_mr_create().
+ *
+ * The global cache must be rebuilt if there's any change and this event has to
+ * be propagated to dataplane threads to flush the local caches.
+ *
+ * @param dev
+ *   Pointer to Ethernet device.
+ * @param addr
+ *   Address of freed memory.
+ * @param len
+ *   Size of freed memory.
+ */
+static void
+mlx5_mr_mem_event_free_cb(struct rte_eth_dev *dev, const void *addr, size_t 
len)
+{
+       struct priv *priv = dev->data->dev_private;
+       const struct rte_memseg_list *msl;
+       struct mlx5_mr *mr;
+       int ms_n;
+       int i;
+       int rebuild = 0;
+
+       DRV_LOG(DEBUG, "port %u free callback: addr=%p, len=%lu",
+               dev->data->port_id, addr, len);
+       msl = rte_mem_virt2memseg_list(addr);
+       /* addr and len must be page-aligned. */
+       assert((uintptr_t)addr == RTE_ALIGN((uintptr_t)addr, msl->page_sz));
+       assert(len == RTE_ALIGN(len, msl->page_sz));
+       ms_n = len / msl->page_sz;
+       rte_rwlock_write_lock(&priv->mr.rwlock);
+       /* Clear bits of freed memsegs from MR. */
+       for (i = 0; i < ms_n; ++i) {
+               const struct rte_memseg *ms;
+               struct mlx5_mr_cache entry;
+               uintptr_t start;
+               int ms_idx;
+               uint32_t pos;
+
+               /* Find MR having this memseg. */
+               start = (uintptr_t)addr + i * msl->page_sz;
+               mr = mr_lookup_dev_list(dev, &entry, start);
+               if (mr == NULL)
+                       continue;
+               ms = rte_mem_virt2memseg((void *)start, msl);
+               assert(ms != NULL);
+               assert(msl->page_sz == ms->hugepage_sz);
+               ms_idx = rte_fbarray_find_idx(&msl->memseg_arr, ms);
+               pos = ms_idx - mr->ms_base_idx;
+               assert(rte_bitmap_get(mr->ms_bmp, pos));
+               assert(pos < mr->ms_bmp_n);
+               DRV_LOG(DEBUG, "port %u MR(%p): clear bitmap[%u] for addr %p",
+                       dev->data->port_id, (void *)mr, pos, (void *)start);
+               rte_bitmap_clear(mr->ms_bmp, pos);
+               if (--mr->ms_n == 0) {
+                       LIST_REMOVE(mr, mr);
+                       LIST_INSERT_HEAD(&priv->mr.mr_free_list, mr, mr);
+                       DRV_LOG(DEBUG, "port %u remove MR(%p) from list",
+                               dev->data->port_id, (void *)mr);
+               }
+               /*
+                * MR is fragmented or will be freed. the global cache must be
+                * rebuilt.
+                */
+               rebuild = 1;
+       }
+       if (rebuild) {
+               mr_rebuild_dev_cache(dev);
+               /*
+                * Flush local caches by propagating invalidation across cores.
+                * rte_smp_wmb() is enough to synchronize this event. If one of
+                * freed memsegs is seen by other core, that means the memseg
+                * has been allocated by allocator, which will come after this
+                * free call. Therefore, this store instruction (incrementing
+                * generation below) will be guaranteed to be seen by other core
+                * before the core sees the newly allocated memory.
+                */
+               ++priv->mr.dev_gen;
+               DRV_LOG(DEBUG, "broadcasting local cache flush, gen=%d",
+                       priv->mr.dev_gen);
+               rte_smp_wmb();
+       }
+       rte_rwlock_write_unlock(&priv->mr.rwlock);
+       if (rebuild && rte_log_get_level(mlx5_logtype) == RTE_LOG_DEBUG)
+               mlx5_mr_dump_dev(dev);
+}
+
+/**
+ * Callback for memory event. This can be called from both primary and 
secondary
+ * process.
+ *
+ * @param event_type
+ *   Memory event type.
+ * @param addr
+ *   Address of memory.
+ * @param len
+ *   Size of memory.
+ */
+void
+mlx5_mr_mem_event_cb(enum rte_mem_event event_type, const void *addr,
+                    size_t len)
+{
+       struct priv *priv;
+       struct mlx5_dev_list *dev_list = &mlx5_shared_data->mem_event_cb_list;
+
+       switch (event_type) {
+       case RTE_MEM_EVENT_FREE:
+               rte_rwlock_write_lock(&mlx5_shared_data->mem_event_rwlock);
+               /* Iterate all the existing mlx5 devices. */
+               LIST_FOREACH(priv, dev_list, mem_event_cb)
+                       mlx5_mr_mem_event_free_cb(eth_dev(priv), addr, len);
+               rte_rwlock_write_unlock(&mlx5_shared_data->mem_event_rwlock);
+               break;
+       case RTE_MEM_EVENT_ALLOC:
+       default:
+               break;
+       }
+}
+
+/**
+ * Look up address in the global MR cache table. If not found, create a new MR.
+ * Insert the found/created entry to local bottom-half cache table.
+ *
+ * @param dev
+ *   Pointer to Ethernet device.
+ * @param mr_ctrl
+ *   Pointer to per-queue MR control structure.
+ * @param[out] entry
+ *   Pointer to returning MR cache entry, found in the global cache or newly
+ *   created. If failed to create one, this is not written.
+ * @param addr
+ *   Search key.
+ *
+ * @return
+ *   Searched LKey on success, UINT32_MAX on no match.
+ */
+static uint32_t
+mlx5_mr_lookup_dev(struct rte_eth_dev *dev, struct mlx5_mr_ctrl *mr_ctrl,
+                  struct mlx5_mr_cache *entry, uintptr_t addr)
+{
+       struct priv *priv = dev->data->dev_private;
+       struct mlx5_mr_btree *bt = &mr_ctrl->cache_bh;
+       uint16_t idx;
+       uint32_t lkey;
+
+       /* If local cache table is full, try to double it. */
+       if (unlikely(bt->len == bt->size))
+               mr_btree_expand(bt, bt->size << 1);
+       /* Look up in the global cache. */
+       rte_rwlock_read_lock(&priv->mr.rwlock);
+       lkey = mr_btree_lookup(&priv->mr.cache, &idx, addr);
+       if (lkey != UINT32_MAX) {
+               /* Found. */
+               *entry = (*priv->mr.cache.table)[idx];
+               rte_rwlock_read_unlock(&priv->mr.rwlock);
+               /*
+                * Update local cache. Even if it fails, return the found entry
+                * to update top-half cache. Next time, this entry will be found
+                * in the global cache.
+                */
+               mr_btree_insert(bt, entry);
+               return lkey;
+       }
+       rte_rwlock_read_unlock(&priv->mr.rwlock);
+       /* First time to see the address? Create a new MR. */
+       lkey = mlx5_mr_create(dev, entry, addr);
+       /*
+        * Update the local cache if successfully created a new global MR. Even
+        * if failed to create one, there's no action to take in this datapath
+        * code. As returning LKey is invalid, this will eventually make HW
+        * fail.
+        */
+       if (lkey != UINT32_MAX)
+               mr_btree_insert(bt, entry);
+       return lkey;
+}
+
+/**
+ * Bottom-half of LKey search on datapath. Firstly search in cache_bh[] and if
+ * misses, search in the global MR cache table and update the new entry to
+ * per-queue local caches.
+ *
+ * @param dev
+ *   Pointer to Ethernet device.
+ * @param mr_ctrl
+ *   Pointer to per-queue MR control structure.
+ * @param addr
+ *   Search key.
+ *
+ * @return
+ *   Searched LKey on success, UINT32_MAX on no match.
+ */
+static uint32_t
+mlx5_mr_addr2mr_bh(struct rte_eth_dev *dev, struct mlx5_mr_ctrl *mr_ctrl,
+                  uintptr_t addr)
+{
+       uint32_t lkey;
+       uint16_t bh_idx = 0;
+       /* Victim in top-half cache to replace with new entry. */
+       struct mlx5_mr_cache *repl = &mr_ctrl->cache[mr_ctrl->head];
+
+       /* Binary-search MR translation table. */
+       lkey = mr_btree_lookup(&mr_ctrl->cache_bh, &bh_idx, addr);
+       /* Update top-half cache. */
+       if (likely(lkey != UINT32_MAX)) {
+               *repl = (*mr_ctrl->cache_bh.table)[bh_idx];
+       } else {
+               /*
+                * If missed in local lookup table, search in the global cache
+                * and local cache_bh[] will be updated inside if possible.
+                * Top-half cache entry will also be updated.
+                */
+               lkey = mlx5_mr_lookup_dev(dev, mr_ctrl, repl, addr);
+               if (unlikely(lkey == UINT32_MAX))
+                       return UINT32_MAX;
+       }
+       /* Update the most recently used entry. */
+       mr_ctrl->mru = mr_ctrl->head;
+       /* Point to the next victim, the oldest. */
+       mr_ctrl->head = (mr_ctrl->head + 1) % MLX5_MR_CACHE_N;
+       return lkey;
+}
+
+/**
+ * Bottom-half of LKey search on Rx.
+ *
+ * @param rxq
+ *   Pointer to Rx queue structure.
+ * @param addr
+ *   Search key.
+ *
+ * @return
+ *   Searched LKey on success, UINT32_MAX on no match.
+ */
+uint32_t
+mlx5_rx_addr2mr_bh(struct mlx5_rxq_data *rxq, uintptr_t addr)
+{
+       struct mlx5_rxq_ctrl *rxq_ctrl =
+               container_of(rxq, struct mlx5_rxq_ctrl, rxq);
+       struct mlx5_mr_ctrl *mr_ctrl = &rxq->mr_ctrl;
+       struct priv *priv = rxq_ctrl->priv;
+
+       DRV_LOG(DEBUG,
+               "Rx queue %u: miss on top-half, mru=%u, head=%u, addr=%p",
+               rxq_ctrl->idx, mr_ctrl->mru, mr_ctrl->head, (void *)addr);
+       return mlx5_mr_addr2mr_bh(eth_dev(priv), mr_ctrl, addr);
+}
+
+/**
+ * Bottom-half of LKey search on Tx.
+ *
+ * @param txq
+ *   Pointer to Tx queue structure.
+ * @param addr
+ *   Search key.
+ *
+ * @return
+ *   Searched LKey on success, UINT32_MAX on no match.
+ */
+uint32_t
+mlx5_tx_addr2mr_bh(struct mlx5_txq_data *txq, uintptr_t addr)
+{
+       struct mlx5_txq_ctrl *txq_ctrl =
+               container_of(txq, struct mlx5_txq_ctrl, txq);
+       struct mlx5_mr_ctrl *mr_ctrl = &txq->mr_ctrl;
+       struct priv *priv = txq_ctrl->priv;
+
+       DRV_LOG(DEBUG,
+               "Tx queue %u: miss on top-half, mru=%u, head=%u, addr=%p",
+               txq_ctrl->idx, mr_ctrl->mru, mr_ctrl->head, (void *)addr);
+       return mlx5_mr_addr2mr_bh(eth_dev(priv), mr_ctrl, addr);
+}
+
+/**
+ * Flush all of the local cache entries.
+ *
+ * @param mr_ctrl
+ *   Pointer to per-queue MR control structure.
+ */
+void
+mlx5_mr_flush_local_cache(struct mlx5_mr_ctrl *mr_ctrl)
+{
+       /* Reset the most-recently-used index. */
+       mr_ctrl->mru = 0;
+       /* Reset the linear search array. */
+       mr_ctrl->head = 0;
+       memset(mr_ctrl->cache, 0, sizeof(mr_ctrl->cache));
+       /* Reset the B-tree table. */
+       mr_ctrl->cache_bh.len = 1;
+       mr_ctrl->cache_bh.overflow = 0;
+       /* Update the generation number. */
+       mr_ctrl->cur_gen = *mr_ctrl->dev_gen_ptr;
+       DRV_LOG(DEBUG, "mr_ctrl(%p): flushed, cur_gen=%d",
+               (void *)mr_ctrl, mr_ctrl->cur_gen);
+}
+
+/* Called during rte_mempool_mem_iter() by mlx5_mr_update_mp(). */
+static void
+mlx5_mr_update_mp_cb(struct rte_mempool *mp __rte_unused, void *opaque,
+                    struct rte_mempool_memhdr *memhdr,
+                    unsigned mem_idx __rte_unused)
+{
+       struct mr_update_mp_data *data = opaque;
+       uint32_t lkey;
+
+       /* Stop iteration if failed in the previous walk. */
+       if (data->ret < 0)
+               return;
+       /* Register address of the chunk and update local caches. */
+       lkey = mlx5_mr_addr2mr_bh(data->dev, data->mr_ctrl,
+                                 (uintptr_t)memhdr->addr);
+       if (lkey == UINT32_MAX)
+               data->ret = -1;
+}
+
+/**
+ * Register entire memory chunks in a Mempool.
+ *
+ * @param dev
+ *   Pointer to Ethernet device.
+ * @param mr_ctrl
+ *   Pointer to per-queue MR control structure.
+ * @param mp
+ *   Pointer to registering Mempool.
+ *
+ * @return
+ *   0 on success, -1 on failure.
+ */
+int
+mlx5_mr_update_mp(struct rte_eth_dev *dev, struct mlx5_mr_ctrl *mr_ctrl,
+                 struct rte_mempool *mp)
+{
+       struct mr_update_mp_data data = {
+               .dev = dev,
+               .mr_ctrl = mr_ctrl,
+               .ret = 0,
+       };
+
+       rte_mempool_mem_iter(mp, mlx5_mr_update_mp_cb, &data);
+       return data.ret;
+}
+
+/**
+ * Dump all the created MRs and the global cache entries.
+ *
+ * @param dev
+ *   Pointer to Ethernet device.
+ */
+void
+mlx5_mr_dump_dev(struct rte_eth_dev *dev)
+{
+       struct priv *priv = dev->data->dev_private;
+       struct mlx5_mr *mr;
+       int mr_n = 0;
+       int chunk_n = 0;
+
+       rte_rwlock_read_lock(&priv->mr.rwlock);
+       /* Iterate all the existing MRs. */
+       LIST_FOREACH(mr, &priv->mr.mr_list, mr) {
+               unsigned int n;
+
+               DRV_LOG(DEBUG,
+                       "port %u MR[%u], LKey = 0x%x, ms_n = %u, ms_bmp_n = %u",
+                       dev->data->port_id, mr_n++,
+                       rte_cpu_to_be_32(mr->ibv_mr->lkey),
+                       mr->ms_n, mr->ms_bmp_n);
+               if (mr->ms_n == 0)
+                       continue;
+               for (n = 0; n < mr->ms_bmp_n; ) {
+                       struct mlx5_mr_cache ret = { 0, };
+
+                       n = mr_find_next_chunk(mr, &ret, n);
+                       if (!ret.end)
+                               break;
+                       DRV_LOG(DEBUG, "  chunk[%u], [0x%lx, 0x%lx)",
+                               chunk_n++, ret.start, ret.end);
+               }
+       }
+       DRV_LOG(DEBUG, "port %u dumping global cache", dev->data->port_id);
+       mlx5_mr_btree_dump(&priv->mr.cache);
+       rte_rwlock_read_unlock(&priv->mr.rwlock);
+}
+
+/**
+ * Release all the created MRs and resources. Remove device from memory 
callback
+ * list.
+ *
+ * @param dev
+ *   Pointer to Ethernet device.
+ */
+void
+mlx5_mr_release(struct rte_eth_dev *dev)
+{
+       struct priv *priv = dev->data->dev_private;
+       struct mlx5_mr *mr_next = LIST_FIRST(&priv->mr.mr_list);
+
+       /* Remove from memory callback device list. */
+       rte_rwlock_write_lock(&mlx5_shared_data->mem_event_rwlock);
+       LIST_REMOVE(priv, mem_event_cb);
+       rte_rwlock_write_unlock(&mlx5_shared_data->mem_event_rwlock);
+       if (rte_log_get_level(mlx5_logtype) == RTE_LOG_DEBUG)
+               mlx5_mr_dump_dev(dev);
+       rte_rwlock_write_lock(&priv->mr.rwlock);
+       /* Detach from MR list and move to free list. */
+       while (mr_next != NULL) {
+               struct mlx5_mr *mr = mr_next;
+
+               mr_next = LIST_NEXT(mr, mr);
+               LIST_REMOVE(mr, mr);
+               LIST_INSERT_HEAD(&priv->mr.mr_free_list, mr, mr);
+       }
+       LIST_INIT(&priv->mr.mr_list);
+       /* Free global cache. */
+       mlx5_mr_btree_free(&priv->mr.cache);
+       rte_rwlock_write_unlock(&priv->mr.rwlock);
+       /* Free all remaining MRs. */
+       mlx5_mr_garbage_collect(dev);
+}
diff --git a/drivers/net/mlx5/mlx5_mr.h b/drivers/net/mlx5/mlx5_mr.h
new file mode 100644
index 000000000..a0a0ef755
--- /dev/null
+++ b/drivers/net/mlx5/mlx5_mr.h
@@ -0,0 +1,121 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright 2018 6WIND S.A.
+ * Copyright 2018 Mellanox Technologies, Ltd
+ */
+
+#ifndef RTE_PMD_MLX5_MR_H_
+#define RTE_PMD_MLX5_MR_H_
+
+#include <stddef.h>
+#include <stdint.h>
+#include <sys/queue.h>
+
+/* Verbs header. */
+/* ISO C doesn't support unnamed structs/unions, disabling -pedantic. */
+#ifdef PEDANTIC
+#pragma GCC diagnostic ignored "-Wpedantic"
+#endif
+#include <infiniband/verbs.h>
+#include <infiniband/mlx5dv.h>
+#ifdef PEDANTIC
+#pragma GCC diagnostic error "-Wpedantic"
+#endif
+
+#include <rte_eal_memconfig.h>
+#include <rte_ethdev.h>
+#include <rte_rwlock.h>
+#include <rte_bitmap.h>
+
+/* Memory Region object. */
+struct mlx5_mr {
+       LIST_ENTRY(mlx5_mr) mr; /**< Pointer to the prev/next entry. */
+       struct ibv_mr *ibv_mr; /* Verbs Memory Region. */
+       const struct rte_memseg_list *msl;
+       int ms_base_idx; /* Start index of msl->memseg_arr[]. */
+       int ms_n; /* Number of memsegs in use. */
+       uint32_t ms_bmp_n; /* Number of bits in memsegs bit-mask. */
+       struct rte_bitmap *ms_bmp; /* Bit-mask of memsegs belonged to MR. */
+};
+
+/* Cache entry for Memory Region. */
+struct mlx5_mr_cache {
+       uintptr_t start; /* Start address of MR. */
+       uintptr_t end; /* End address of MR. */
+       uint32_t lkey; /* rte_cpu_to_be_32(ibv_mr->lkey). */
+} __rte_packed;
+
+/* MR Cache table for Binary search. */
+struct mlx5_mr_btree {
+       uint16_t len; /* Number of entries. */
+       uint16_t size; /* Total number of entries. */
+       int overflow; /* Mark failure of table expansion. */
+       struct mlx5_mr_cache (*table)[];
+} __rte_packed;
+
+/* Per-queue MR control descriptor. */
+struct mlx5_mr_ctrl {
+       uint32_t *dev_gen_ptr; /* Generation number of device to poll. */
+       uint32_t cur_gen; /* Generation number saved to flush caches. */
+       uint16_t mru; /* Index of last hit entry in top-half cache. */
+       uint16_t head; /* Index of the oldest entry in top-half cache. */
+       struct mlx5_mr_cache cache[MLX5_MR_CACHE_N]; /* Cache for top-half. */
+       struct mlx5_mr_btree cache_bh; /* Cache for bottom-half. */
+} __rte_packed;
+
+/* First entry must be NULL for comparison. */
+#define MR_N(n) ((n) - 1)
+
+/* Whether there's only one entry in MR lookup table. */
+#define IS_SINGLE_MR(n) (MR_N(n) == 1)
+
+extern struct mlx5_dev_list  mlx5_mem_event_cb_list;
+extern rte_rwlock_t mlx5_mem_event_rwlock;
+
+void mlx5_mr_free(struct rte_eth_dev *dev, struct mlx5_mr *mr);
+int mlx5_mr_btree_init(struct mlx5_mr_btree *bt, int n, int socket);
+void mlx5_mr_btree_free(struct mlx5_mr_btree *bt);
+void mlx5_mr_mem_event_cb(enum rte_mem_event event_type, const void *addr,
+                         size_t len);
+int mlx5_mr_update_mp(struct rte_eth_dev *dev, struct mlx5_mr_ctrl *mr_ctrl,
+                     struct rte_mempool *mp);
+void mlx5_mr_dump_dev(struct rte_eth_dev *dev);
+void mlx5_mr_release(struct rte_eth_dev *dev);
+
+/**
+ * Look up LKey from given lookup table by linear search. Firstly look up the
+ * last-hit entry. If miss, the entire array is searched. If found, update the
+ * last-hit index and return LKey.
+ *
+ * @param lkp_tbl
+ *   Pointer to lookup table.
+ * @param[in,out] cached_idx
+ *   Pointer to last-hit index.
+ * @param n
+ *   Size of lookup table.
+ * @param addr
+ *   Search key.
+ *
+ * @return
+ *   Searched LKey on success, UINT32_MAX on no match.
+ */
+static __rte_always_inline uint32_t
+mlx5_mr_lookup_cache(struct mlx5_mr_cache *lkp_tbl, uint16_t *cached_idx,
+                    uint16_t n, uintptr_t addr)
+{
+       uint16_t idx;
+
+       if (likely(addr >= lkp_tbl[*cached_idx].start &&
+                  addr < lkp_tbl[*cached_idx].end))
+               return lkp_tbl[*cached_idx].lkey;
+       for (idx = 0; idx < n && lkp_tbl[idx].start != 0; ++idx) {
+               if (addr >= lkp_tbl[idx].start &&
+                   addr < lkp_tbl[idx].end) {
+                       /* Found. */
+                       *cached_idx = idx;
+                       return lkp_tbl[idx].lkey;
+               }
+       }
+       return UINT32_MAX;
+}
+
+#endif /* RTE_PMD_MLX5_MR_H_ */
diff --git a/drivers/net/mlx5/mlx5_rxq.c b/drivers/net/mlx5/mlx5_rxq.c
index d4fe1fed7..22e2f9673 100644
--- a/drivers/net/mlx5/mlx5_rxq.c
+++ b/drivers/net/mlx5/mlx5_rxq.c
@@ -789,7 +789,7 @@ mlx5_rxq_ibv_new(struct rte_eth_dev *dev, uint16_t idx)
                        .addr = rte_cpu_to_be_64(rte_pktmbuf_mtod(buf,
                                                                  uintptr_t)),
                        .byte_count = rte_cpu_to_be_32(DATA_LEN(buf)),
-                       .lkey = UINT32_MAX,
+                       .lkey = mlx5_rx_mb2mr(rxq_data, buf),
                };
        }
        rxq_data->rq_db = rwq.dbrec;
@@ -967,6 +967,11 @@ mlx5_rxq_new(struct rte_eth_dev *dev, uint16_t idx, 
uint16_t desc,
                rte_errno = ENOMEM;
                return NULL;
        }
+       if (mlx5_mr_btree_init(&tmpl->rxq.mr_ctrl.cache_bh,
+                              MLX5_MR_BTREE_CACHE_N, socket)) {
+               /* rte_errno is already set. */
+               goto error;
+       }
        tmpl->socket = socket;
        if (dev->data->dev_conf.intr_conf.rxq)
                tmpl->irq = 1;
@@ -1120,6 +1125,7 @@ mlx5_rxq_release(struct rte_eth_dev *dev, uint16_t idx)
                DRV_LOG(DEBUG, "port %u Rx queue %u: refcnt %d",
                        dev->data->port_id, rxq_ctrl->idx,
                        rte_atomic32_read(&rxq_ctrl->refcnt));
+               mlx5_mr_btree_free(&rxq_ctrl->rxq.mr_ctrl.cache_bh);
                LIST_REMOVE(rxq_ctrl, next);
                rte_free(rxq_ctrl);
                (*priv->rxqs)[idx] = NULL;
diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index 56c243495..8a863c157 100644
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -1965,6 +1965,9 @@ mlx5_rx_burst(void *dpdk_rxq, struct rte_mbuf **pkts, 
uint16_t pkts_n)
                 * changes.
                 */
                wqe->addr = rte_cpu_to_be_64(rte_pktmbuf_mtod(rep, uintptr_t));
+               /* If there's only one MR, no need to replace LKey in WQE. */
+               if (unlikely(!IS_SINGLE_MR(rxq->mr_ctrl.cache_bh.len)))
+                       wqe->lkey = mlx5_rx_mb2mr(rxq, rep);
                if (len > DATA_LEN(seg)) {
                        len -= DATA_LEN(seg);
                        ++NB_SEGS(pkt);
diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h
index e8cad51aa..74581cf9b 100644
--- a/drivers/net/mlx5/mlx5_rxtx.h
+++ b/drivers/net/mlx5/mlx5_rxtx.h
@@ -29,6 +29,7 @@
 
 #include "mlx5_utils.h"
 #include "mlx5.h"
+#include "mlx5_mr.h"
 #include "mlx5_autoconf.h"
 #include "mlx5_defs.h"
 #include "mlx5_prm.h"
@@ -81,6 +82,7 @@ struct mlx5_rxq_data {
        uint16_t rq_ci;
        uint16_t rq_pi;
        uint16_t cq_ci;
+       struct mlx5_mr_ctrl mr_ctrl; /* MR control descriptor. */
        volatile struct mlx5_wqe_data_seg(*wqes)[];
        volatile struct mlx5_cqe(*cqes)[];
        struct rxq_zip zip; /* Compressed context. */
@@ -109,8 +111,8 @@ struct mlx5_rxq_ibv {
 struct mlx5_rxq_ctrl {
        LIST_ENTRY(mlx5_rxq_ctrl) next; /* Pointer to the next element. */
        rte_atomic32_t refcnt; /* Reference counter. */
-       struct priv *priv; /* Back pointer to private data. */
        struct mlx5_rxq_ibv *ibv; /* Verbs elements. */
+       struct priv *priv; /* Back pointer to private data. */
        struct mlx5_rxq_data rxq; /* Data path structure. */
        unsigned int socket; /* CPU socket ID for allocations. */
        uint32_t tunnel_types[16]; /* Tunnel type counter. */
@@ -165,6 +167,7 @@ struct mlx5_txq_data {
        uint16_t inline_max_packet_sz; /* Max packet size for inlining. */
        uint32_t qp_num_8s; /* QP number shifted by 8. */
        uint64_t offloads; /* Offloads for Tx Queue. */
+       struct mlx5_mr_ctrl mr_ctrl; /* MR control descriptor. */
        volatile struct mlx5_cqe (*cqes)[]; /* Completion queue. */
        volatile void *wqes; /* Work queue (use volatile to write into). */
        volatile uint32_t *qp_db; /* Work queue doorbell. */
@@ -187,11 +190,11 @@ struct mlx5_txq_ibv {
 struct mlx5_txq_ctrl {
        LIST_ENTRY(mlx5_txq_ctrl) next; /* Pointer to the next element. */
        rte_atomic32_t refcnt; /* Reference counter. */
-       struct priv *priv; /* Back pointer to private data. */
        unsigned int socket; /* CPU socket ID for allocations. */
        unsigned int max_inline_data; /* Max inline data. */
        unsigned int max_tso_header; /* Max TSO header size. */
        struct mlx5_txq_ibv *ibv; /* Verbs queue object. */
+       struct priv *priv; /* Back pointer to private data. */
        struct mlx5_txq_data txq; /* Data path structure. */
        off_t uar_mmap_offset; /* UAR mmap offset for non-primary process. */
        volatile void *bf_reg_orig; /* Blueflame register from verbs. */
@@ -308,6 +311,12 @@ uint16_t mlx5_tx_burst_vec(void *dpdk_txq, struct rte_mbuf 
**pkts,
 uint16_t mlx5_rx_burst_vec(void *dpdk_txq, struct rte_mbuf **pkts,
                           uint16_t pkts_n);
 
+/* mlx5_mr.c */
+
+void mlx5_mr_flush_local_cache(struct mlx5_mr_ctrl *mr_ctrl);
+uint32_t mlx5_rx_addr2mr_bh(struct mlx5_rxq_data *rxq, uintptr_t addr);
+uint32_t mlx5_tx_addr2mr_bh(struct mlx5_txq_data *txq, uintptr_t addr);
+
 #ifndef NDEBUG
 /**
  * Verify or set magic value in CQE.
@@ -493,14 +502,66 @@ mlx5_tx_complete(struct mlx5_txq_data *txq)
        *txq->cq_db = rte_cpu_to_be_32(cq_ci);
 }
 
+/**
+ * Query LKey from a packet buffer for Rx. No need to flush local caches for Rx
+ * as mempool is pre-configured and static.
+ *
+ * @param rxq
+ *   Pointer to Rx queue structure.
+ * @param addr
+ *   Address to search.
+ *
+ * @return
+ *   Searched LKey on success, UINT32_MAX on no match.
+ */
 static __rte_always_inline uint32_t
-mlx5_tx_mb2mr(struct mlx5_txq_data *txq, struct rte_mbuf *mb)
+mlx5_rx_addr2mr(struct mlx5_rxq_data *rxq, uintptr_t addr)
 {
-       (void)txq;
-       (void)mb;
-       return UINT32_MAX;
+       struct mlx5_mr_ctrl *mr_ctrl = &rxq->mr_ctrl;
+       uint32_t lkey;
+
+       /* Linear search on MR cache array. */
+       lkey = mlx5_mr_lookup_cache(mr_ctrl->cache, &mr_ctrl->mru,
+                                   MLX5_MR_CACHE_N, addr);
+       if (likely(lkey != UINT32_MAX))
+               return lkey;
+       /* Take slower bottom-half (Binary Search) on miss. */
+       return mlx5_rx_addr2mr_bh(rxq, addr);
 }
 
+#define mlx5_rx_mb2mr(rxq, mb) mlx5_rx_addr2mr(rxq, 
(uintptr_t)((mb)->buf_addr))
+
+/**
+ * Query LKey from a packet buffer for Tx. If not found, add the mempool.
+ *
+ * @param txq
+ *   Pointer to Tx queue structure.
+ * @param addr
+ *   Address to search.
+ *
+ * @return
+ *   Searched LKey on success, UINT32_MAX on no match.
+ */
+static __rte_always_inline uint32_t
+mlx5_tx_addr2mr(struct mlx5_txq_data *txq, uintptr_t addr)
+{
+       struct mlx5_mr_ctrl *mr_ctrl = &txq->mr_ctrl;
+       uint32_t lkey;
+
+       /* Check generation bit to see if there's any change on existing MRs. */
+       if (unlikely(*mr_ctrl->dev_gen_ptr != mr_ctrl->cur_gen))
+               mlx5_mr_flush_local_cache(mr_ctrl);
+       /* Linear search on MR cache array. */
+       lkey = mlx5_mr_lookup_cache(mr_ctrl->cache, &mr_ctrl->mru,
+                                   MLX5_MR_CACHE_N, addr);
+       if (likely(lkey != UINT32_MAX))
+               return lkey;
+       /* Take slower bottom-half (binary search) on miss. */
+       return mlx5_tx_addr2mr_bh(txq, addr);
+}
+
+#define mlx5_tx_mb2mr(rxq, mb) mlx5_tx_addr2mr(rxq, 
(uintptr_t)((mb)->buf_addr))
+
 /**
  * Ring TX queue doorbell and flush the update if requested.
  *
diff --git a/drivers/net/mlx5/mlx5_rxtx_vec.h b/drivers/net/mlx5/mlx5_rxtx_vec.h
index 56c5a1b0c..76678a820 100644
--- a/drivers/net/mlx5/mlx5_rxtx_vec.h
+++ b/drivers/net/mlx5/mlx5_rxtx_vec.h
@@ -99,9 +99,13 @@ mlx5_rx_replenish_bulk_mbuf(struct mlx5_rxq_data *rxq, 
uint16_t n)
                rxq->stats.rx_nombuf += n;
                return;
        }
-       for (i = 0; i < n; ++i)
+       for (i = 0; i < n; ++i) {
                wq[i].addr = rte_cpu_to_be_64((uintptr_t)elts[i]->buf_addr +
                                              RTE_PKTMBUF_HEADROOM);
+               /* If there's only one MR, no need to replace LKey in WQE. */
+               if (unlikely(!IS_SINGLE_MR(rxq->mr_ctrl.cache_bh.len)))
+                       wq[i].lkey = mlx5_rx_mb2mr(rxq, elts[i]);
+       }
        rxq->rq_ci += n;
        /* Prevent overflowing into consumed mbufs. */
        elts_idx = rxq->rq_ci & q_mask;
diff --git a/drivers/net/mlx5/mlx5_trigger.c b/drivers/net/mlx5/mlx5_trigger.c
index 3db6c3f35..36b7c9e2f 100644
--- a/drivers/net/mlx5/mlx5_trigger.c
+++ b/drivers/net/mlx5/mlx5_trigger.c
@@ -104,9 +104,18 @@ mlx5_rxq_start(struct rte_eth_dev *dev)
 
        for (i = 0; i != priv->rxqs_n; ++i) {
                struct mlx5_rxq_ctrl *rxq_ctrl = mlx5_rxq_get(dev, i);
+               struct rte_mempool *mp;
 
                if (!rxq_ctrl)
                        continue;
+               /* Pre-register Rx mempool. */
+               mp = rxq_ctrl->rxq.mp;
+               DRV_LOG(DEBUG,
+                       "port %u Rx queue %u registering"
+                       " mp %s having %u chunks",
+                       dev->data->port_id, rxq_ctrl->idx,
+                       mp->name, mp->nb_mem_chunks);
+               mlx5_mr_update_mp(dev, &rxq_ctrl->rxq.mr_ctrl, mp);
                ret = rxq_alloc_elts(rxq_ctrl);
                if (ret)
                        goto error;
@@ -154,6 +163,8 @@ mlx5_dev_start(struct rte_eth_dev *dev)
                        dev->data->port_id, strerror(rte_errno));
                goto error;
        }
+       if (rte_log_get_level(mlx5_logtype) == RTE_LOG_DEBUG)
+               mlx5_mr_dump_dev(dev);
        ret = mlx5_rx_intr_vec_enable(dev);
        if (ret) {
                DRV_LOG(ERR, "port %u Rx interrupt vector creation failed",
diff --git a/drivers/net/mlx5/mlx5_txq.c b/drivers/net/mlx5/mlx5_txq.c
index a71f3d0f0..9ce6f2098 100644
--- a/drivers/net/mlx5/mlx5_txq.c
+++ b/drivers/net/mlx5/mlx5_txq.c
@@ -804,6 +804,13 @@ mlx5_txq_new(struct rte_eth_dev *dev, uint16_t idx, 
uint16_t desc,
                rte_errno = ENOMEM;
                return NULL;
        }
+       if (mlx5_mr_btree_init(&tmpl->txq.mr_ctrl.cache_bh,
+                              MLX5_MR_BTREE_CACHE_N, socket)) {
+               /* rte_errno is already set. */
+               goto error;
+       }
+       /* Save pointer of global generation number to check memory event. */
+       tmpl->txq.mr_ctrl.dev_gen_ptr = &priv->mr.dev_gen;
        assert(desc > MLX5_TX_COMP_THRESH);
        tmpl->txq.offloads = conf->offloads;
        tmpl->priv = priv;
@@ -823,6 +830,9 @@ mlx5_txq_new(struct rte_eth_dev *dev, uint16_t idx, 
uint16_t desc,
                idx, rte_atomic32_read(&tmpl->refcnt));
        LIST_INSERT_HEAD(&priv->txqsctrl, tmpl, next);
        return tmpl;
+error:
+       rte_free(tmpl);
+       return NULL;
 }
 
 /**
@@ -882,6 +892,7 @@ mlx5_txq_release(struct rte_eth_dev *dev, uint16_t idx)
                        dev->data->port_id, txq->idx,
                        rte_atomic32_read(&txq->refcnt));
                txq_free_elts(txq);
+               mlx5_mr_btree_free(&txq->txq.mr_ctrl.cache_bh);
                LIST_REMOVE(txq, next);
                rte_free(txq);
                (*priv->txqs)[idx] = NULL;
-- 
2.11.0

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