hw/rdma: Implementation of generic rdma device layers

This layer is composed of two sub-modules, backend and resource manager.
Backend sub-module is responsible for all the interaction with IB layers
such as ibverbs and umad (external libraries).
Resource manager is a collection of functions and structures to manage
RDMA resources such as QPs, CQs and MRs.

Reviewed-by: Dotan Barak <dotanb@mellanox.com>
Reviewed-by: Zhu Yanjun <yanjun.zhu@oracle.com>
Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>

1 files changed, 818 insertions, 0 deletions

diff --git a/hw/rdma/rdma_backend.c b/hw/rdma/rdma_backend.c
new file mode 100644
index 0000000000..e306fba534
--- /dev/null
+++ b/hw/rdma/rdma_backend.c
@@ -0,0 +1,818 @@
+/*
+ * QEMU paravirtual RDMA - Generic RDMA backend
+ *
+ * Copyright (C) 2018 Oracle
+ * Copyright (C) 2018 Red Hat Inc
+ *
+ * Authors:
+ *     Yuval Shaia <yuval.shaia@oracle.com>
+ *     Marcel Apfelbaum <marcel@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include <qemu/osdep.h>
+#include <qemu/error-report.h>
+#include <qapi/error.h>
+
+#include <infiniband/verbs.h>
+
+#include "trace.h"
+#include "rdma_utils.h"
+#include "rdma_rm.h"
+#include "rdma_backend.h"
+
+/* Vendor Errors */
+#define VENDOR_ERR_FAIL_BACKEND     0x201
+#define VENDOR_ERR_TOO_MANY_SGES    0x202
+#define VENDOR_ERR_NOMEM            0x203
+#define VENDOR_ERR_QP0              0x204
+#define VENDOR_ERR_NO_SGE           0x205
+#define VENDOR_ERR_MAD_SEND         0x206
+#define VENDOR_ERR_INVLKEY          0x207
+#define VENDOR_ERR_MR_SMALL         0x208
+
+#define THR_NAME_LEN 16
+
+typedef struct BackendCtx {
+    uint64_t req_id;
+    void *up_ctx;
+    bool is_tx_req;
+} BackendCtx;
+
+static void (*comp_handler)(int status, unsigned int vendor_err, void *ctx);
+
+static void dummy_comp_handler(int status, unsigned int vendor_err, void *ctx)
+{
+    pr_err("No completion handler is registered\n");
+}
+
+static void poll_cq(RdmaDeviceResources *rdma_dev_res, struct ibv_cq *ibcq)
+{
+    int i, ne;
+    BackendCtx *bctx;
+    struct ibv_wc wc[2];
+
+    pr_dbg("Entering poll_cq loop on cq %p\n", ibcq);
+    do {
+        ne = ibv_poll_cq(ibcq, ARRAY_SIZE(wc), wc);
+
+        pr_dbg("Got %d completion(s) from cq %p\n", ne, ibcq);
+
+        for (i = 0; i < ne; i++) {
+            pr_dbg("wr_id=0x%lx\n", wc[i].wr_id);
+            pr_dbg("status=%d\n", wc[i].status);
+
+            bctx = rdma_rm_get_cqe_ctx(rdma_dev_res, wc[i].wr_id);
+            if (unlikely(!bctx)) {
+                pr_dbg("Error: Failed to find ctx for req %ld\n", wc[i].wr_id);
+                continue;
+            }
+            pr_dbg("Processing %s CQE\n", bctx->is_tx_req ? "send" : "recv");
+
+            comp_handler(wc[i].status, wc[i].vendor_err, bctx->up_ctx);
+
+            rdma_rm_dealloc_cqe_ctx(rdma_dev_res, wc[i].wr_id);
+            g_free(bctx);
+        }
+    } while (ne > 0);
+
+    if (ne < 0) {
+        pr_dbg("Got error %d from ibv_poll_cq\n", ne);
+    }
+}
+
+static void *comp_handler_thread(void *arg)
+{
+    RdmaBackendDev *backend_dev = (RdmaBackendDev *)arg;
+    int rc;
+    struct ibv_cq *ev_cq;
+    void *ev_ctx;
+
+    pr_dbg("Starting\n");
+
+    while (backend_dev->comp_thread.run) {
+        pr_dbg("Waiting for completion on channel %p\n", backend_dev->channel);
+        rc = ibv_get_cq_event(backend_dev->channel, &ev_cq, &ev_ctx);
+        pr_dbg("ibv_get_cq_event=%d\n", rc);
+        if (unlikely(rc)) {
+            pr_dbg("---> ibv_get_cq_event (%d)\n", rc);
+            continue;
+        }
+
+        rc = ibv_req_notify_cq(ev_cq, 0);
+        if (unlikely(rc)) {
+            pr_dbg("Error %d from ibv_req_notify_cq\n", rc);
+        }
+
+        poll_cq(backend_dev->rdma_dev_res, ev_cq);
+
+        ibv_ack_cq_events(ev_cq, 1);
+    }
+
+    pr_dbg("Going down\n");
+
+    /* TODO: Post cqe for all remaining buffs that were posted */
+
+    return NULL;
+}
+
+void rdma_backend_register_comp_handler(void (*handler)(int status,
+                                        unsigned int vendor_err, void *ctx))
+{
+    comp_handler = handler;
+}
+
+void rdma_backend_unregister_comp_handler(void)
+{
+    rdma_backend_register_comp_handler(dummy_comp_handler);
+}
+
+int rdma_backend_query_port(RdmaBackendDev *backend_dev,
+                            struct ibv_port_attr *port_attr)
+{
+    int rc;
+
+    rc = ibv_query_port(backend_dev->context, backend_dev->port_num, port_attr);
+    if (rc) {
+        pr_dbg("Error %d from ibv_query_port\n", rc);
+        return -EIO;
+    }
+
+    return 0;
+}
+
+void rdma_backend_poll_cq(RdmaDeviceResources *rdma_dev_res, RdmaBackendCQ *cq)
+{
+    poll_cq(rdma_dev_res, cq->ibcq);
+}
+
+static GHashTable *ah_hash;
+
+static struct ibv_ah *create_ah(RdmaBackendDev *backend_dev, struct ibv_pd *pd,
+                                uint8_t sgid_idx, union ibv_gid *dgid)
+{
+    GBytes *ah_key = g_bytes_new(dgid, sizeof(*dgid));
+    struct ibv_ah *ah = g_hash_table_lookup(ah_hash, ah_key);
+
+    if (ah) {
+        trace_create_ah_cache_hit(be64_to_cpu(dgid->global.subnet_prefix),
+                                  be64_to_cpu(dgid->global.interface_id));
+        g_bytes_unref(ah_key);
+    } else {
+        struct ibv_ah_attr ah_attr = {
+            .is_global     = 1,
+            .port_num      = backend_dev->port_num,
+            .grh.hop_limit = 1,
+        };
+
+        ah_attr.grh.dgid = *dgid;
+        ah_attr.grh.sgid_index = sgid_idx;
+
+        ah = ibv_create_ah(pd, &ah_attr);
+        if (ah) {
+            g_hash_table_insert(ah_hash, ah_key, ah);
+        } else {
+            g_bytes_unref(ah_key);
+            pr_dbg("ibv_create_ah failed for gid <%lx %lx>\n",
+                    be64_to_cpu(dgid->global.subnet_prefix),
+                    be64_to_cpu(dgid->global.interface_id));
+        }
+
+        trace_create_ah_cache_miss(be64_to_cpu(dgid->global.subnet_prefix),
+                                   be64_to_cpu(dgid->global.interface_id));
+    }
+
+    return ah;
+}
+
+static void destroy_ah_hash_key(gpointer data)
+{
+    g_bytes_unref(data);
+}
+
+static void destroy_ah_hast_data(gpointer data)
+{
+    struct ibv_ah *ah = data;
+
+    ibv_destroy_ah(ah);
+}
+
+static void ah_cache_init(void)
+{
+    ah_hash = g_hash_table_new_full(g_bytes_hash, g_bytes_equal,
+                                    destroy_ah_hash_key, destroy_ah_hast_data);
+}
+
+static int build_host_sge_array(RdmaDeviceResources *rdma_dev_res,
+                                struct ibv_sge *dsge, struct ibv_sge *ssge,
+                                uint8_t num_sge)
+{
+    RdmaRmMR *mr;
+    int ssge_idx;
+
+    pr_dbg("num_sge=%d\n", num_sge);
+
+    for (ssge_idx = 0; ssge_idx < num_sge; ssge_idx++) {
+        mr = rdma_rm_get_mr(rdma_dev_res, ssge[ssge_idx].lkey);
+        if (unlikely(!mr)) {
+            pr_dbg("Invalid lkey 0x%x\n", ssge[ssge_idx].lkey);
+            return VENDOR_ERR_INVLKEY | ssge[ssge_idx].lkey;
+        }
+
+        dsge->addr = mr->user_mr.host_virt + ssge[ssge_idx].addr -
+                     mr->user_mr.guest_start;
+        dsge->length = ssge[ssge_idx].length;
+        dsge->lkey = rdma_backend_mr_lkey(&mr->backend_mr);
+
+        pr_dbg("ssge->addr=0x%lx\n", (uint64_t)ssge[ssge_idx].addr);
+        pr_dbg("dsge->addr=0x%lx\n", dsge->addr);
+        pr_dbg("dsge->length=%d\n", dsge->length);
+        pr_dbg("dsge->lkey=0x%x\n", dsge->lkey);
+
+        dsge++;
+    }
+
+    return 0;
+}
+
+void rdma_backend_post_send(RdmaBackendDev *backend_dev,
+                            RdmaBackendQP *qp, uint8_t qp_type,
+                            struct ibv_sge *sge, uint32_t num_sge,
+                            union ibv_gid *dgid, uint32_t dqpn,
+                            uint32_t dqkey, void *ctx)
+{
+    BackendCtx *bctx;
+    struct ibv_sge new_sge[MAX_SGE];
+    uint32_t bctx_id;
+    int rc;
+    struct ibv_send_wr wr = {0}, *bad_wr;
+
+    if (!qp->ibqp) { /* This field does not get initialized for QP0 and QP1 */
+        if (qp_type == IBV_QPT_SMI) {
+            pr_dbg("QP0 unsupported\n");
+            comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_QP0, ctx);
+        } else if (qp_type == IBV_QPT_GSI) {
+            pr_dbg("QP1\n");
+            comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_MAD_SEND, ctx);
+        }
+        pr_dbg("qp->ibqp is NULL for qp_type %d!!!\n", qp_type);
+        return;
+    }
+
+    pr_dbg("num_sge=%d\n", num_sge);
+    if (!num_sge) {
+        pr_dbg("num_sge=0\n");
+        comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_NO_SGE, ctx);
+        return;
+    }
+
+    bctx = g_malloc0(sizeof(*bctx));
+    bctx->up_ctx = ctx;
+    bctx->is_tx_req = 1;
+
+    rc = rdma_rm_alloc_cqe_ctx(backend_dev->rdma_dev_res, &bctx_id, bctx);
+    if (unlikely(rc)) {
+        pr_dbg("Failed to allocate cqe_ctx\n");
+        comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_NOMEM, ctx);
+        goto out_free_bctx;
+    }
+
+    rc = build_host_sge_array(backend_dev->rdma_dev_res, new_sge, sge, num_sge);
+    if (rc) {
+        pr_dbg("Error: Failed to build host SGE array\n");
+        comp_handler(IBV_WC_GENERAL_ERR, rc, ctx);
+        goto out_dealloc_cqe_ctx;
+    }
+
+    if (qp_type == IBV_QPT_UD) {
+        wr.wr.ud.ah = create_ah(backend_dev, qp->ibpd,
+                                backend_dev->backend_gid_idx, dgid);
+        wr.wr.ud.remote_qpn = dqpn;
+        wr.wr.ud.remote_qkey = dqkey;
+    }
+
+    wr.num_sge = num_sge;
+    wr.opcode = IBV_WR_SEND;
+    wr.send_flags = IBV_SEND_SIGNALED;
+    wr.sg_list = new_sge;
+    wr.wr_id = bctx_id;
+
+    rc = ibv_post_send(qp->ibqp, &wr, &bad_wr);
+    pr_dbg("ibv_post_send=%d\n", rc);
+    if (rc) {
+        pr_dbg("Fail (%d, %d) to post send WQE to qpn %d\n", rc, errno,
+                qp->ibqp->qp_num);
+        comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_FAIL_BACKEND, ctx);
+        goto out_dealloc_cqe_ctx;
+    }
+
+    return;
+
+out_dealloc_cqe_ctx:
+    rdma_rm_dealloc_cqe_ctx(backend_dev->rdma_dev_res, bctx_id);
+
+out_free_bctx:
+    g_free(bctx);
+}
+
+void rdma_backend_post_recv(RdmaBackendDev *backend_dev,
+                            RdmaDeviceResources *rdma_dev_res,
+                            RdmaBackendQP *qp, uint8_t qp_type,
+                            struct ibv_sge *sge, uint32_t num_sge, void *ctx)
+{
+    BackendCtx *bctx;
+    struct ibv_sge new_sge[MAX_SGE];
+    uint32_t bctx_id;
+    int rc;
+    struct ibv_recv_wr wr = {0}, *bad_wr;
+
+    if (!qp->ibqp) { /* This field does not get initialized for QP0 and QP1 */
+        if (qp_type == IBV_QPT_SMI) {
+            pr_dbg("QP0 unsupported\n");
+            comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_QP0, ctx);
+        }
+        if (qp_type == IBV_QPT_GSI) {
+            pr_dbg("QP1\n");
+            comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_MAD_SEND, ctx);
+        }
+        return;
+    }
+
+    pr_dbg("num_sge=%d\n", num_sge);
+    if (!num_sge) {
+        pr_dbg("num_sge=0\n");
+        comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_NO_SGE, ctx);
+        return;
+    }
+
+    bctx = g_malloc0(sizeof(*bctx));
+    bctx->up_ctx = ctx;
+    bctx->is_tx_req = 0;
+
+    rc = rdma_rm_alloc_cqe_ctx(rdma_dev_res, &bctx_id, bctx);
+    if (unlikely(rc)) {
+        pr_dbg("Failed to allocate cqe_ctx\n");
+        comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_NOMEM, ctx);
+        goto out_free_bctx;
+    }
+
+    rc = build_host_sge_array(rdma_dev_res, new_sge, sge, num_sge);
+    if (rc) {
+        pr_dbg("Error: Failed to build host SGE array\n");
+        comp_handler(IBV_WC_GENERAL_ERR, rc, ctx);
+        goto out_dealloc_cqe_ctx;
+    }
+
+    wr.num_sge = num_sge;
+    wr.sg_list = new_sge;
+    wr.wr_id = bctx_id;
+    rc = ibv_post_recv(qp->ibqp, &wr, &bad_wr);
+    pr_dbg("ibv_post_recv=%d\n", rc);
+    if (rc) {
+        pr_dbg("Fail (%d, %d) to post recv WQE to qpn %d\n", rc, errno,
+                qp->ibqp->qp_num);
+        comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_FAIL_BACKEND, ctx);
+        goto out_dealloc_cqe_ctx;
+    }
+
+    return;
+
+out_dealloc_cqe_ctx:
+    rdma_rm_dealloc_cqe_ctx(rdma_dev_res, bctx_id);
+
+out_free_bctx:
+    g_free(bctx);
+}
+
+int rdma_backend_create_pd(RdmaBackendDev *backend_dev, RdmaBackendPD *pd)
+{
+    pd->ibpd = ibv_alloc_pd(backend_dev->context);
+
+    return pd->ibpd ? 0 : -EIO;
+}
+
+void rdma_backend_destroy_pd(RdmaBackendPD *pd)
+{
+    if (pd->ibpd) {
+        ibv_dealloc_pd(pd->ibpd);
+    }
+}
+
+int rdma_backend_create_mr(RdmaBackendMR *mr, RdmaBackendPD *pd, uint64_t addr,
+                           size_t length, int access)
+{
+    pr_dbg("addr=0x%lx\n", addr);
+    pr_dbg("len=%ld\n", length);
+    mr->ibmr = ibv_reg_mr(pd->ibpd, (void *)addr, length, access);
+    if (mr->ibmr) {
+        pr_dbg("lkey=0x%x\n", mr->ibmr->lkey);
+        pr_dbg("rkey=0x%x\n", mr->ibmr->rkey);
+        mr->ibpd = pd->ibpd;
+    }
+
+    return mr->ibmr ? 0 : -EIO;
+}
+
+void rdma_backend_destroy_mr(RdmaBackendMR *mr)
+{
+    if (mr->ibmr) {
+        ibv_dereg_mr(mr->ibmr);
+    }
+}
+
+int rdma_backend_create_cq(RdmaBackendDev *backend_dev, RdmaBackendCQ *cq,
+                           int cqe)
+{
+    int rc;
+
+    pr_dbg("cqe=%d\n", cqe);
+
+    pr_dbg("dev->channel=%p\n", backend_dev->channel);
+    cq->ibcq = ibv_create_cq(backend_dev->context, cqe + 1, NULL,
+                             backend_dev->channel, 0);
+
+    if (cq->ibcq) {
+        rc = ibv_req_notify_cq(cq->ibcq, 0);
+        if (rc) {
+            pr_dbg("Error %d from ibv_req_notify_cq\n", rc);
+        }
+        cq->backend_dev = backend_dev;
+    }
+
+    return cq->ibcq ? 0 : -EIO;
+}
+
+void rdma_backend_destroy_cq(RdmaBackendCQ *cq)
+{
+    if (cq->ibcq) {
+        ibv_destroy_cq(cq->ibcq);
+    }
+}
+
+int rdma_backend_create_qp(RdmaBackendQP *qp, uint8_t qp_type,
+                           RdmaBackendPD *pd, RdmaBackendCQ *scq,
+                           RdmaBackendCQ *rcq, uint32_t max_send_wr,
+                           uint32_t max_recv_wr, uint32_t max_send_sge,
+                           uint32_t max_recv_sge)
+{
+    struct ibv_qp_init_attr attr = {0};
+
+    qp->ibqp = 0;
+    pr_dbg("qp_type=%d\n", qp_type);
+
+    switch (qp_type) {
+    case IBV_QPT_GSI:
+        pr_dbg("QP1 unsupported\n");
+        return 0;
+
+    case IBV_QPT_RC:
+        /* fall through */
+    case IBV_QPT_UD:
+        /* do nothing */
+        break;
+
+    default:
+        pr_dbg("Unsupported QP type %d\n", qp_type);
+        return -EIO;
+    }
+
+    attr.qp_type = qp_type;
+    attr.send_cq = scq->ibcq;
+    attr.recv_cq = rcq->ibcq;
+    attr.cap.max_send_wr = max_send_wr;
+    attr.cap.max_recv_wr = max_recv_wr;
+    attr.cap.max_send_sge = max_send_sge;
+    attr.cap.max_recv_sge = max_recv_sge;
+
+    pr_dbg("max_send_wr=%d\n", max_send_wr);
+    pr_dbg("max_recv_wr=%d\n", max_recv_wr);
+    pr_dbg("max_send_sge=%d\n", max_send_sge);
+    pr_dbg("max_recv_sge=%d\n", max_recv_sge);
+
+    qp->ibqp = ibv_create_qp(pd->ibpd, &attr);
+    if (likely(!qp->ibqp)) {
+        pr_dbg("Error from ibv_create_qp\n");
+        return -EIO;
+    }
+
+    qp->ibpd = pd->ibpd;
+
+    /* TODO: Query QP to get max_inline_data and save it to be used in send */
+
+    pr_dbg("qpn=0x%x\n", qp->ibqp->qp_num);
+
+    return 0;
+}
+
+int rdma_backend_qp_state_init(RdmaBackendDev *backend_dev, RdmaBackendQP *qp,
+                               uint8_t qp_type, uint32_t qkey)
+{
+    struct ibv_qp_attr attr = {0};
+    int rc, attr_mask;
+
+    pr_dbg("qpn=0x%x\n", qp->ibqp->qp_num);
+    pr_dbg("sport_num=%d\n", backend_dev->port_num);
+
+    attr_mask = IBV_QP_STATE | IBV_QP_PKEY_INDEX | IBV_QP_PORT;
+    attr.qp_state        = IBV_QPS_INIT;
+    attr.pkey_index      = 0;
+    attr.port_num        = backend_dev->port_num;
+
+    switch (qp_type) {
+    case IBV_QPT_RC:
+        attr_mask |= IBV_QP_ACCESS_FLAGS;
+        break;
+
+    case IBV_QPT_UD:
+        attr.qkey = qkey;
+        attr_mask |= IBV_QP_QKEY;
+        break;
+
+    default:
+        pr_dbg("Unsupported QP type %d\n", qp_type);
+        return -EIO;
+    }
+
+    rc = ibv_modify_qp(qp->ibqp, &attr, attr_mask);
+    if (rc) {
+        pr_dbg("Error %d from ibv_modify_qp\n", rc);
+        return -EIO;
+    }
+
+    return 0;
+}
+
+int rdma_backend_qp_state_rtr(RdmaBackendDev *backend_dev, RdmaBackendQP *qp,
+                              uint8_t qp_type, union ibv_gid *dgid,
+                              uint32_t dqpn, uint32_t rq_psn, uint32_t qkey,
+                              bool use_qkey)
+{
+    struct ibv_qp_attr attr = {0};
+    union ibv_gid ibv_gid = {
+        .global.interface_id = dgid->global.interface_id,
+        .global.subnet_prefix = dgid->global.subnet_prefix
+    };
+    int rc, attr_mask;
+
+    attr.qp_state = IBV_QPS_RTR;
+    attr_mask = IBV_QP_STATE;
+
+    switch (qp_type) {
+    case IBV_QPT_RC:
+        pr_dbg("dgid=0x%lx,%lx\n",
+               be64_to_cpu(ibv_gid.global.subnet_prefix),
+               be64_to_cpu(ibv_gid.global.interface_id));
+        pr_dbg("dqpn=0x%x\n", dqpn);
+        pr_dbg("sgid_idx=%d\n", backend_dev->backend_gid_idx);
+        pr_dbg("sport_num=%d\n", backend_dev->port_num);
+        pr_dbg("rq_psn=0x%x\n", rq_psn);
+
+        attr.path_mtu               = IBV_MTU_1024;
+        attr.dest_qp_num            = dqpn;
+        attr.max_dest_rd_atomic     = 1;
+        attr.min_rnr_timer          = 12;
+        attr.ah_attr.port_num       = backend_dev->port_num;
+        attr.ah_attr.is_global      = 1;
+        attr.ah_attr.grh.hop_limit  = 1;
+        attr.ah_attr.grh.dgid       = ibv_gid;
+        attr.ah_attr.grh.sgid_index = backend_dev->backend_gid_idx;
+        attr.rq_psn                 = rq_psn;
+
+        attr_mask |= IBV_QP_AV | IBV_QP_PATH_MTU | IBV_QP_DEST_QPN |
+                     IBV_QP_RQ_PSN | IBV_QP_MAX_DEST_RD_ATOMIC |
+                     IBV_QP_MIN_RNR_TIMER;
+        break;
+
+    case IBV_QPT_UD:
+        if (use_qkey) {
+            pr_dbg("qkey=0x%x\n", qkey);
+            attr.qkey = qkey;
+            attr_mask |= IBV_QP_QKEY;
+        }
+        break;
+    }
+
+    rc = ibv_modify_qp(qp->ibqp, &attr, attr_mask);
+    if (rc) {
+        pr_dbg("Error %d from ibv_modify_qp\n", rc);
+        return -EIO;
+    }
+
+    return 0;
+}
+
+int rdma_backend_qp_state_rts(RdmaBackendQP *qp, uint8_t qp_type,
+                              uint32_t sq_psn, uint32_t qkey, bool use_qkey)
+{
+    struct ibv_qp_attr attr = {0};
+    int rc, attr_mask;
+
+    pr_dbg("qpn=0x%x\n", qp->ibqp->qp_num);
+    pr_dbg("sq_psn=0x%x\n", sq_psn);
+
+    attr.qp_state = IBV_QPS_RTS;
+    attr.sq_psn = sq_psn;
+    attr_mask = IBV_QP_STATE | IBV_QP_SQ_PSN;
+
+    switch (qp_type) {
+    case IBV_QPT_RC:
+        attr.timeout       = 14;
+        attr.retry_cnt     = 7;
+        attr.rnr_retry     = 7;
+        attr.max_rd_atomic = 1;
+
+        attr_mask |= IBV_QP_TIMEOUT | IBV_QP_RETRY_CNT | IBV_QP_RNR_RETRY |
+                     IBV_QP_MAX_QP_RD_ATOMIC;
+        break;
+
+    case IBV_QPT_UD:
+        if (use_qkey) {
+            pr_dbg("qkey=0x%x\n", qkey);
+            attr.qkey = qkey;
+            attr_mask |= IBV_QP_QKEY;
+        }
+        break;
+    }
+
+    rc = ibv_modify_qp(qp->ibqp, &attr, attr_mask);
+    if (rc) {
+        pr_dbg("Error %d from ibv_modify_qp\n", rc);
+        return -EIO;
+    }
+
+    return 0;
+}
+
+void rdma_backend_destroy_qp(RdmaBackendQP *qp)
+{
+    if (qp->ibqp) {
+        ibv_destroy_qp(qp->ibqp);
+    }
+}
+
+#define CHK_ATTR(req, dev, member, fmt) ({ \
+    pr_dbg("%s="fmt","fmt"\n", #member, dev.member, req->member); \
+    if (req->member > dev.member) { \
+        warn_report("%s = 0x%lx is higher than host device capability 0x%lx", \
+                    #member, (uint64_t)req->member, (uint64_t)dev.member); \
+        req->member = dev.member; \
+    } \
+    pr_dbg("%s="fmt"\n", #member, req->member); })
+
+static int init_device_caps(RdmaBackendDev *backend_dev,
+                            struct ibv_device_attr *dev_attr)
+{
+    if (ibv_query_device(backend_dev->context, &backend_dev->dev_attr)) {
+        return -EIO;
+    }
+
+    CHK_ATTR(dev_attr, backend_dev->dev_attr, max_mr_size, "%ld");
+    CHK_ATTR(dev_attr, backend_dev->dev_attr, max_qp, "%d");
+    CHK_ATTR(dev_attr, backend_dev->dev_attr, max_sge, "%d");
+    CHK_ATTR(dev_attr, backend_dev->dev_attr, max_qp_wr, "%d");
+    CHK_ATTR(dev_attr, backend_dev->dev_attr, max_cq, "%d");
+    CHK_ATTR(dev_attr, backend_dev->dev_attr, max_cqe, "%d");
+    CHK_ATTR(dev_attr, backend_dev->dev_attr, max_mr, "%d");
+    CHK_ATTR(dev_attr, backend_dev->dev_attr, max_pd, "%d");
+    CHK_ATTR(dev_attr, backend_dev->dev_attr, max_qp_rd_atom, "%d");
+    CHK_ATTR(dev_attr, backend_dev->dev_attr, max_qp_init_rd_atom, "%d");
+    CHK_ATTR(dev_attr, backend_dev->dev_attr, max_ah, "%d");
+
+    return 0;
+}
+
+int rdma_backend_init(RdmaBackendDev *backend_dev,
+                      RdmaDeviceResources *rdma_dev_res,
+                      const char *backend_device_name, uint8_t port_num,
+                      uint8_t backend_gid_idx, struct ibv_device_attr *dev_attr,
+                      Error **errp)
+{
+    int i;
+    int ret = 0;
+    int num_ibv_devices;
+    char thread_name[THR_NAME_LEN] = {0};
+    struct ibv_device **dev_list;
+    struct ibv_port_attr port_attr;
+
+    backend_dev->backend_gid_idx = backend_gid_idx;
+    backend_dev->port_num = port_num;
+    backend_dev->rdma_dev_res = rdma_dev_res;
+
+    rdma_backend_register_comp_handler(dummy_comp_handler);
+
+    dev_list = ibv_get_device_list(&num_ibv_devices);
+    if (!dev_list) {
+        error_setg(errp, "Failed to get IB devices list");
+        return -EIO;
+    }
+
+    if (num_ibv_devices == 0) {
+        error_setg(errp, "No IB devices were found");
+        ret = -ENXIO;
+        goto out_free_dev_list;
+    }
+
+    if (backend_device_name) {
+        for (i = 0; dev_list[i]; ++i) {
+            if (!strcmp(ibv_get_device_name(dev_list[i]),
+                        backend_device_name)) {
+                break;
+            }
+        }
+
+        backend_dev->ib_dev = dev_list[i];
+        if (!backend_dev->ib_dev) {
+            error_setg(errp, "Failed to find IB device %s",
+                       backend_device_name);
+            ret = -EIO;
+            goto out_free_dev_list;
+        }
+    } else {
+        backend_dev->ib_dev = *dev_list;
+    }
+
+    pr_dbg("Using backend device %s, port %d, gid_idx %d\n",
+           ibv_get_device_name(backend_dev->ib_dev),
+           backend_dev->port_num, backend_dev->backend_gid_idx);
+
+    backend_dev->context = ibv_open_device(backend_dev->ib_dev);
+    if (!backend_dev->context) {
+        error_setg(errp, "Failed to open IB device");
+        ret = -EIO;
+        goto out;
+    }
+
+    backend_dev->channel = ibv_create_comp_channel(backend_dev->context);
+    if (!backend_dev->channel) {
+        error_setg(errp, "Failed to create IB communication channel");
+        ret = -EIO;
+        goto out_close_device;
+    }
+    pr_dbg("dev->backend_dev.channel=%p\n", backend_dev->channel);
+
+    ret = ibv_query_port(backend_dev->context, backend_dev->port_num,
+                         &port_attr);
+    if (ret) {
+        error_setg(errp, "Error %d from ibv_query_port", ret);
+        ret = -EIO;
+        goto out_destroy_comm_channel;
+    }
+
+    if (backend_dev->backend_gid_idx > port_attr.gid_tbl_len) {
+        error_setg(errp, "Invalid backend_gid_idx, should be less than %d",
+                   port_attr.gid_tbl_len);
+        goto out_destroy_comm_channel;
+    }
+
+    ret = init_device_caps(backend_dev, dev_attr);
+    if (ret) {
+        error_setg(errp, "Failed to initialize device capabilities");
+        ret = -EIO;
+        goto out_destroy_comm_channel;
+    }
+
+    ret = ibv_query_gid(backend_dev->context, backend_dev->port_num,
+                         backend_dev->backend_gid_idx, &backend_dev->gid);
+    if (ret) {
+        error_setg(errp, "Failed to query gid %d",
+                   backend_dev->backend_gid_idx);
+        ret = -EIO;
+        goto out_destroy_comm_channel;
+    }
+    pr_dbg("subnet_prefix=0x%lx\n",
+           be64_to_cpu(backend_dev->gid.global.subnet_prefix));
+    pr_dbg("interface_id=0x%lx\n",
+           be64_to_cpu(backend_dev->gid.global.interface_id));
+
+    snprintf(thread_name, sizeof(thread_name), "rdma_comp_%s",
+             ibv_get_device_name(backend_dev->ib_dev));
+    backend_dev->comp_thread.run = true;
+    qemu_thread_create(&backend_dev->comp_thread.thread, thread_name,
+                       comp_handler_thread, backend_dev, QEMU_THREAD_DETACHED);
+
+    ah_cache_init();
+
+    goto out_free_dev_list;
+
+out_destroy_comm_channel:
+    ibv_destroy_comp_channel(backend_dev->channel);
+
+out_close_device:
+    ibv_close_device(backend_dev->context);
+
+out_free_dev_list:
+    ibv_free_device_list(dev_list);
+
+out:
+    return ret;
+}
+
+void rdma_backend_fini(RdmaBackendDev *backend_dev)
+{
+    g_hash_table_destroy(ah_hash);
+    ibv_destroy_comp_channel(backend_dev->channel);
+    ibv_close_device(backend_dev->context);
+}