[PATCH RFC v2 2/4] vdpa/mlx5: implement .reset_map driver op

[Si-Wei Liu <si-wei.liu@oracle.com>]

Today, mlx5_vdpa gets started by preallocate 1:1 DMA mapping at
device creation time, while this 1:1 mapping will be implicitly
destroyed when the first .set_map call is invoked. Everytime
when the .reset callback is invoked, any mapping left behind will
be dropped then reset back to the initial 1:1 DMA mapping.

In order to reduce excessive memory mapping cost during live
migration, it is desirable to decouple the vhost-vdpa iotlb
abstraction from the virtio device life cycle, i.e. mappings
should be left intact across virtio device reset. Leverage the
.reset_map callback to reset memory mapping, then the device
.reset routine can run free from having to clean up memory
mappings.

Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>

---
RFC v1 -> v2:
  - fix error path when both CVQ and DVQ fall in same asid
---
 drivers/vdpa/mlx5/core/mlx5_vdpa.h |  1 +
 drivers/vdpa/mlx5/core/mr.c        | 70 +++++++++++++++++++++++---------------
 drivers/vdpa/mlx5/net/mlx5_vnet.c  | 18 +++++++---
 3 files changed, 56 insertions(+), 33 deletions(-)

diff --git a/drivers/vdpa/mlx5/core/mlx5_vdpa.h b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
index b53420e..5c9a25a 100644
--- a/drivers/vdpa/mlx5/core/mlx5_vdpa.h
+++ b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
@@ -123,6 +123,7 @@ int mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb *iotlb,
 			unsigned int asid);
 void mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev);
 void mlx5_vdpa_destroy_mr_asid(struct mlx5_vdpa_dev *mvdev, unsigned int asid);
+int mlx5_vdpa_reset_mr(struct mlx5_vdpa_dev *mvdev, unsigned int asid);
 
 #define mlx5_vdpa_warn(__dev, format, ...)                                                         \
 	dev_warn((__dev)->mdev->device, "%s:%d:(pid %d) warning: " format, __func__, __LINE__,     \
diff --git a/drivers/vdpa/mlx5/core/mr.c b/drivers/vdpa/mlx5/core/mr.c
index 5a1971fc..ec2c7b4e1 100644
--- a/drivers/vdpa/mlx5/core/mr.c
+++ b/drivers/vdpa/mlx5/core/mr.c
@@ -489,21 +489,15 @@ static void destroy_user_mr(struct mlx5_vdpa_dev *mvdev, struct mlx5_vdpa_mr *mr
 	}
 }
 
-static void _mlx5_vdpa_destroy_cvq_mr(struct mlx5_vdpa_dev *mvdev, unsigned int asid)
+static void _mlx5_vdpa_destroy_cvq_mr(struct mlx5_vdpa_dev *mvdev)
 {
-	if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] != asid)
-		return;
-
 	prune_iotlb(mvdev);
 }
 
-static void _mlx5_vdpa_destroy_dvq_mr(struct mlx5_vdpa_dev *mvdev, unsigned int asid)
+static void _mlx5_vdpa_destroy_dvq_mr(struct mlx5_vdpa_dev *mvdev)
 {
 	struct mlx5_vdpa_mr *mr = &mvdev->mr;
 
-	if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] != asid)
-		return;
-
 	if (!mr->initialized)
 		return;
 
@@ -521,8 +515,10 @@ void mlx5_vdpa_destroy_mr_asid(struct mlx5_vdpa_dev *mvdev, unsigned int asid)
 
 	mutex_lock(&mr->mkey_mtx);
 
-	_mlx5_vdpa_destroy_dvq_mr(mvdev, asid);
-	_mlx5_vdpa_destroy_cvq_mr(mvdev, asid);
+	if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid)
+		_mlx5_vdpa_destroy_dvq_mr(mvdev);
+	if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] == asid)
+		_mlx5_vdpa_destroy_cvq_mr(mvdev);
 
 	mutex_unlock(&mr->mkey_mtx);
 }
@@ -534,25 +530,17 @@ void mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev)
 }
 
 static int _mlx5_vdpa_create_cvq_mr(struct mlx5_vdpa_dev *mvdev,
-				    struct vhost_iotlb *iotlb,
-				    unsigned int asid)
+				    struct vhost_iotlb *iotlb)
 {
-	if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] != asid)
-		return 0;
-
 	return dup_iotlb(mvdev, iotlb);
 }
 
 static int _mlx5_vdpa_create_dvq_mr(struct mlx5_vdpa_dev *mvdev,
-				    struct vhost_iotlb *iotlb,
-				    unsigned int asid)
+				    struct vhost_iotlb *iotlb)
 {
 	struct mlx5_vdpa_mr *mr = &mvdev->mr;
 	int err;
 
-	if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] != asid)
-		return 0;
-
 	if (mr->initialized)
 		return 0;
 
@@ -574,18 +562,22 @@ static int _mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev,
 {
 	int err;
 
-	err = _mlx5_vdpa_create_dvq_mr(mvdev, iotlb, asid);
-	if (err)
-		return err;
-
-	err = _mlx5_vdpa_create_cvq_mr(mvdev, iotlb, asid);
-	if (err)
-		goto out_err;
+	if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid) {
+		err = _mlx5_vdpa_create_dvq_mr(mvdev, iotlb);
+		if (err)
+			return err;
+	}
+	if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] == asid) {
+		err = _mlx5_vdpa_create_cvq_mr(mvdev, iotlb);
+		if (err)
+			goto out_err;
+	}
 
 	return 0;
 
 out_err:
-	_mlx5_vdpa_destroy_dvq_mr(mvdev, asid);
+	if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid)
+		_mlx5_vdpa_destroy_dvq_mr(mvdev);
 
 	return err;
 }
@@ -601,6 +593,28 @@ int mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb *iotlb,
 	return err;
 }
 
+int mlx5_vdpa_reset_mr(struct mlx5_vdpa_dev *mvdev, unsigned int asid)
+{
+	struct mlx5_vdpa_mr *mr = &mvdev->mr;
+	int err = 0;
+
+	if (asid != 0)
+		return 0;
+
+	mutex_lock(&mr->mkey_mtx);
+	if (!mr->user_mr)
+		goto out;
+	_mlx5_vdpa_destroy_dvq_mr(mvdev);
+	if (MLX5_CAP_GEN(mvdev->mdev, umem_uid_0)) {
+		err = _mlx5_vdpa_create_dvq_mr(mvdev, NULL);
+		if (err)
+			mlx5_vdpa_warn(mvdev, "create DMA MR failed\n");
+	}
+out:
+	mutex_unlock(&mr->mkey_mtx);
+	return err;
+}
+
 int mlx5_vdpa_handle_set_map(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb *iotlb,
 			     bool *change_map, unsigned int asid)
 {
diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index 37be945..3cb5db6 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -2824,7 +2824,6 @@ static int mlx5_vdpa_reset(struct vdpa_device *vdev)
 	unregister_link_notifier(ndev);
 	teardown_driver(ndev);
 	clear_vqs_ready(ndev);
-	mlx5_vdpa_destroy_mr(&ndev->mvdev);
 	ndev->mvdev.status = 0;
 	ndev->mvdev.suspended = false;
 	ndev->cur_num_vqs = 0;
@@ -2835,10 +2834,6 @@ static int mlx5_vdpa_reset(struct vdpa_device *vdev)
 	init_group_to_asid_map(mvdev);
 	++mvdev->generation;
 
-	if (MLX5_CAP_GEN(mvdev->mdev, umem_uid_0)) {
-		if (mlx5_vdpa_create_mr(mvdev, NULL, 0))
-			mlx5_vdpa_warn(mvdev, "create MR failed\n");
-	}
 	up_write(&ndev->reslock);
 
 	return 0;
@@ -2903,6 +2898,18 @@ static int mlx5_vdpa_set_map(struct vdpa_device *vdev, unsigned int asid,
 	return err;
 }
 
+static int mlx5_vdpa_reset_map(struct vdpa_device *vdev, unsigned int asid)
+{
+	struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
+	struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
+	int err;
+
+	down_write(&ndev->reslock);
+	err = mlx5_vdpa_reset_mr(mvdev, asid);
+	up_write(&ndev->reslock);
+	return err;
+}
+
 static struct device *mlx5_get_vq_dma_dev(struct vdpa_device *vdev, u16 idx)
 {
 	struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
@@ -3162,6 +3169,7 @@ static int mlx5_set_group_asid(struct vdpa_device *vdev, u32 group,
 	.set_config = mlx5_vdpa_set_config,
 	.get_generation = mlx5_vdpa_get_generation,
 	.set_map = mlx5_vdpa_set_map,
+	.reset_map = mlx5_vdpa_reset_map,
 	.set_group_asid = mlx5_set_group_asid,
 	.get_vq_dma_dev = mlx5_get_vq_dma_dev,
 	.free = mlx5_vdpa_free,
-- 
1.8.3.1

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