IB/mlx5: Create UMR QP just before first reg_mr occurs

UMR QP is not used in some cases, so move QP and its CQ creations from
driver load flow to the time first reg_mr occurs, that is when MR
interfaces are first called.

The initialization of dev->umrc.pd and dev->umrc.lock is still done in
driver load because pd is needed for mlx5_mkey_cache_init and the lock
is reused to protect against the concurrent creation.

When testing 4G bytes memory registration latency with rtool [1] and 8
threads in parallel, there is minor performance degradation (<5% for
the max latency) is seen for the first reg_mr with this change.

Link: https://github.com/paravmellanox/rtool [1]

Signed-off-by: Jianbo Liu <[email protected]>
Link: https://lore.kernel.org/r/55d3c4f8a542fd974d8a4c5816eccfb318a59b38.1717409369.git.leon@kernel.org
Signed-off-by: Leon Romanovsky <[email protected]>

drivers/infiniband/hw/mlx5/main.c

@@ -4086,6 +4086,7 @@ static void mlx5_ib_stage_pre_ib_reg_umr_cleanup(struct mlx5_ib_dev *dev)
 {
 	mlx5_mkey_cache_cleanup(dev);
 	mlx5r_umr_resource_cleanup(dev);
+	mlx5r_umr_cleanup(dev);
 }
 
 static void mlx5_ib_stage_ib_reg_cleanup(struct mlx5_ib_dev *dev)
@@ -4097,7 +4098,7 @@ static int mlx5_ib_stage_post_ib_reg_umr_init(struct mlx5_ib_dev *dev)
 {
 	int ret;
 
-	ret = mlx5r_umr_resource_init(dev);
+	ret = mlx5r_umr_init(dev);
 	if (ret)
 		return ret;
 

drivers/infiniband/hw/mlx5/mlx5_ib.h

@@ -751,6 +751,8 @@ struct umr_common {
 	 */
 	struct mutex lock;
 	unsigned int state;
+	/* Protects from repeat UMR QP creation */
+	struct mutex init_lock;
 };
 
 #define NUM_MKEYS_PER_PAGE \

drivers/infiniband/hw/mlx5/mr.c

@@ -1470,13 +1470,18 @@ struct ib_mr *mlx5_ib_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
 {
 	struct mlx5_ib_dev *dev = to_mdev(pd->device);
 	struct ib_umem *umem;
+	int err;
 
 	if (!IS_ENABLED(CONFIG_INFINIBAND_USER_MEM))
 		return ERR_PTR(-EOPNOTSUPP);
 
 	mlx5_ib_dbg(dev, "start 0x%llx, iova 0x%llx, length 0x%llx, access_flags 0x%x\n",
 		    start, iova, length, access_flags);
 
+	err = mlx5r_umr_resource_init(dev);
+	if (err)
+		return ERR_PTR(err);
+
 	if (access_flags & IB_ACCESS_ON_DEMAND)
 		return create_user_odp_mr(pd, start, length, iova, access_flags,
 					  udata);
@@ -1523,6 +1528,10 @@ struct ib_mr *mlx5_ib_reg_user_mr_dmabuf(struct ib_pd *pd, u64 offset,
 		    "offset 0x%llx, virt_addr 0x%llx, length 0x%llx, fd %d, access_flags 0x%x\n",
 		    offset, virt_addr, length, fd, access_flags);
 
+	err = mlx5r_umr_resource_init(dev);
+	if (err)
+		return ERR_PTR(err);
+
 	/* dmabuf requires xlt update via umr to work. */
 	if (!mlx5r_umr_can_load_pas(dev, length))
 		return ERR_PTR(-EINVAL);

drivers/infiniband/hw/mlx5/umr.c

@@ -135,22 +135,28 @@ static int mlx5r_umr_qp_rst2rts(struct mlx5_ib_dev *dev, struct ib_qp *qp)
 int mlx5r_umr_resource_init(struct mlx5_ib_dev *dev)
 {
 	struct ib_qp_init_attr init_attr = {};
-	struct ib_pd *pd;
 	struct ib_cq *cq;
 	struct ib_qp *qp;
-	int ret;
+	int ret = 0;
 
-	pd = ib_alloc_pd(&dev->ib_dev, 0);
-	if (IS_ERR(pd)) {
-		mlx5_ib_dbg(dev, "Couldn't create PD for sync UMR QP\n");
-		return PTR_ERR(pd);
-	}
+
+	/*
+	 * UMR qp is set once, never changed until device unload.
+	 * Avoid taking the mutex if initialization is already done.
+	 */
+	if (dev->umrc.qp)
+		return 0;
+
+	mutex_lock(&dev->umrc.init_lock);
+	/* First user allocates the UMR resources. Skip if already allocated. */
+	if (dev->umrc.qp)
+		goto unlock;
 
 	cq = ib_alloc_cq(&dev->ib_dev, NULL, 128, 0, IB_POLL_SOFTIRQ);
 	if (IS_ERR(cq)) {
 		mlx5_ib_dbg(dev, "Couldn't create CQ for sync UMR QP\n");
 		ret = PTR_ERR(cq);
-		goto destroy_pd;
+		goto unlock;
 	}
 
 	init_attr.send_cq = cq;
@@ -160,7 +166,7 @@ int mlx5r_umr_resource_init(struct mlx5_ib_dev *dev)
 	init_attr.cap.max_send_sge = 1;
 	init_attr.qp_type = MLX5_IB_QPT_REG_UMR;
 	init_attr.port_num = 1;
-	qp = ib_create_qp(pd, &init_attr);
+	qp = ib_create_qp(dev->umrc.pd, &init_attr);
 	if (IS_ERR(qp)) {
 		mlx5_ib_dbg(dev, "Couldn't create sync UMR QP\n");
 		ret = PTR_ERR(qp);
@@ -171,31 +177,54 @@ int mlx5r_umr_resource_init(struct mlx5_ib_dev *dev)
 	if (ret)
 		goto destroy_qp;
 
-	dev->umrc.qp = qp;
 	dev->umrc.cq = cq;
-	dev->umrc.pd = pd;
 
 	sema_init(&dev->umrc.sem, MAX_UMR_WR);
 	mutex_init(&dev->umrc.lock);
 	dev->umrc.state = MLX5_UMR_STATE_ACTIVE;
+	dev->umrc.qp = qp;
 
+	mutex_unlock(&dev->umrc.init_lock);
 	return 0;
 
 destroy_qp:
 	ib_destroy_qp(qp);
 destroy_cq:
 	ib_free_cq(cq);
-destroy_pd:
-	ib_dealloc_pd(pd);
+unlock:
+	mutex_unlock(&dev->umrc.init_lock);
 	return ret;
 }
 
 void mlx5r_umr_resource_cleanup(struct mlx5_ib_dev *dev)
 {
 	if (dev->umrc.state == MLX5_UMR_STATE_UNINIT)
 		return;
+	mutex_destroy(&dev->umrc.lock);
+	/* After device init, UMR cp/qp are not unset during the lifetime. */
 	ib_destroy_qp(dev->umrc.qp);
 	ib_free_cq(dev->umrc.cq);
+}
+
+int mlx5r_umr_init(struct mlx5_ib_dev *dev)
+{
+	struct ib_pd *pd;
+
+	pd = ib_alloc_pd(&dev->ib_dev, 0);
+	if (IS_ERR(pd)) {
+		mlx5_ib_dbg(dev, "Couldn't create PD for sync UMR QP\n");
+		return PTR_ERR(pd);
+	}
+	dev->umrc.pd = pd;
+
+	mutex_init(&dev->umrc.init_lock);
+
+	return 0;
+}
+
+void mlx5r_umr_cleanup(struct mlx5_ib_dev *dev)
+{
+	mutex_destroy(&dev->umrc.init_lock);
 	ib_dealloc_pd(dev->umrc.pd);
 }
 

drivers/infiniband/hw/mlx5/umr.h

@@ -16,6 +16,9 @@
 int mlx5r_umr_resource_init(struct mlx5_ib_dev *dev);
 void mlx5r_umr_resource_cleanup(struct mlx5_ib_dev *dev);
 
+int mlx5r_umr_init(struct mlx5_ib_dev *dev);
+void mlx5r_umr_cleanup(struct mlx5_ib_dev *dev);
+
 static inline bool mlx5r_umr_can_load_pas(struct mlx5_ib_dev *dev,
 					  size_t length)
 {