[Qemu-devel] [PATCH PULL 3/4] hw/rdma: Skip data-path mr_id translation

[Marcel Apfelbaum <marcel.apfelbaum@gmail.com>]

From: Yuval Shaia <yuval.shaia.ml@gmail.com>

With the change made in commit 68b89aee71 ("Utilize ibv_reg_mr_iova for
memory registration") the MR emulation is no longer needed in order to
translate the guest addresses into host addresses.
With that, the next obvious step is to skip entirely the processing in
data-path.
To accomplish this, return the backend's lkey to driver so we will not
need to do the emulated mr_id to backend mr_id translation in data-path.

The function build_host_sge_array is still called in data-path but only
for backward computability with statistics collection.

While there, as a cosmetic change to make the code cleaner - make one
copy of the function rdma_backend_create_mr and leave the redundant
guest_start argument in the legacy code.

Signed-off-by: Yuval Shaia <yuval.shaia.ml@gmail.com>
Reviewed-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Message-Id: <20200320143429.9490-3-yuval.shaia.ml@gmail.com>
Signed-off-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
---
 hw/rdma/rdma_backend.c | 21 ++++++++++++++-------
 hw/rdma/rdma_backend.h |  5 -----
 hw/rdma/rdma_rm.c      | 13 ++++++-------
 3 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/hw/rdma/rdma_backend.c b/hw/rdma/rdma_backend.c
index b7ffbef9c0..3dd39fe1a7 100644
--- a/hw/rdma/rdma_backend.c
+++ b/hw/rdma/rdma_backend.c
@@ -377,6 +377,7 @@ static void ah_cache_init(void)
                                     destroy_ah_hash_key, destroy_ah_hast_data);
 }
 
+#ifdef LEGACY_RDMA_REG_MR
 static int build_host_sge_array(RdmaDeviceResources *rdma_dev_res,
                                 struct ibv_sge *sge, uint8_t num_sge,
                                 uint64_t *total_length)
@@ -391,9 +392,7 @@ static int build_host_sge_array(RdmaDeviceResources *rdma_dev_res,
             return VENDOR_ERR_INVLKEY | sge[idx].lkey;
         }
 
-#ifdef LEGACY_RDMA_REG_MR
         sge[idx].addr = (uintptr_t)mr->virt + sge[idx].addr - mr->start;
-#endif
         sge[idx].lkey = rdma_backend_mr_lkey(&mr->backend_mr);
 
         *total_length += sge[idx].length;
@@ -401,6 +400,19 @@ static int build_host_sge_array(RdmaDeviceResources *rdma_dev_res,
 
     return 0;
 }
+#else
+static inline int build_host_sge_array(RdmaDeviceResources *rdma_dev_res,
+                                       struct ibv_sge *sge, uint8_t num_sge,
+                                       uint64_t *total_length)
+{
+    int idx;
+
+    for (idx = 0; idx < num_sge; idx++) {
+        *total_length += sge[idx].length;
+    }
+    return 0;
+}
+#endif
 
 static void trace_mad_message(const char *title, char *buf, int len)
 {
@@ -731,13 +743,8 @@ void rdma_backend_destroy_pd(RdmaBackendPD *pd)
     }
 }
 
-#ifdef LEGACY_RDMA_REG_MR
-int rdma_backend_create_mr(RdmaBackendMR *mr, RdmaBackendPD *pd, void *addr,
-                           size_t length, int access)
-#else
 int rdma_backend_create_mr(RdmaBackendMR *mr, RdmaBackendPD *pd, void *addr,
                            size_t length, uint64_t guest_start, int access)
-#endif
 {
 #ifdef LEGACY_RDMA_REG_MR
     mr->ibmr = ibv_reg_mr(pd->ibpd, addr, length, access);
diff --git a/hw/rdma/rdma_backend.h b/hw/rdma/rdma_backend.h
index 127f96e2d5..225af481e0 100644
--- a/hw/rdma/rdma_backend.h
+++ b/hw/rdma/rdma_backend.h
@@ -78,13 +78,8 @@ int rdma_backend_query_port(RdmaBackendDev *backend_dev,
 int rdma_backend_create_pd(RdmaBackendDev *backend_dev, RdmaBackendPD *pd);
 void rdma_backend_destroy_pd(RdmaBackendPD *pd);
 
-#ifdef LEGACY_RDMA_REG_MR
-int rdma_backend_create_mr(RdmaBackendMR *mr, RdmaBackendPD *pd, void *addr,
-                           size_t length, int access);
-#else
 int rdma_backend_create_mr(RdmaBackendMR *mr, RdmaBackendPD *pd, void *addr,
                            size_t length, uint64_t guest_start, int access);
-#endif
 void rdma_backend_destroy_mr(RdmaBackendMR *mr);
 
 int rdma_backend_create_cq(RdmaBackendDev *backend_dev, RdmaBackendCQ *cq,
diff --git a/hw/rdma/rdma_rm.c b/hw/rdma/rdma_rm.c
index 1524dfaeaa..7e9ea283c9 100644
--- a/hw/rdma/rdma_rm.c
+++ b/hw/rdma/rdma_rm.c
@@ -227,21 +227,20 @@ int rdma_rm_alloc_mr(RdmaDeviceResources *dev_res, uint32_t pd_handle,
         mr->length = guest_length;
         mr->virt += (mr->start & (TARGET_PAGE_SIZE - 1));
 
-#ifdef LEGACY_RDMA_REG_MR
-        ret = rdma_backend_create_mr(&mr->backend_mr, &pd->backend_pd, mr->virt,
-                                     mr->length, access_flags);
-#else
         ret = rdma_backend_create_mr(&mr->backend_mr, &pd->backend_pd, mr->virt,
                                      mr->length, guest_start, access_flags);
-#endif
         if (ret) {
             ret = -EIO;
             goto out_dealloc_mr;
         }
+#ifdef LEGACY_RDMA_REG_MR
+        /* We keep mr_handle in lkey so send and recv get get mr ptr */
+        *lkey = *mr_handle;
+#else
+        *lkey = rdma_backend_mr_lkey(&mr->backend_mr);
+#endif
     }
 
-    /* We keep mr_handle in lkey so send and recv get get mr ptr */
-    *lkey = *mr_handle;
     *rkey = -1;
 
     mr->pd_handle = pd_handle;
-- 
2.17.2