Re: [PATCH 2/2] vdpa/mlx5: Add support for running with virtio_vdpa

Jason Wang <jasowang@xxxxxxxxxx> · Mon, 31 May 2021 14:44:35 +0800

在 2021/5/31 下午1:13, Eli Cohen 写道:
On Mon, May 31, 2021 at 11:16:11AM +0800, Jason Wang wrote:
在 2021/5/30 下午3:54, Eli Cohen 写道:
In order to support running vdpa using vritio_vdpa driver, we need  to
create a different kind of MR, one that has 1:1 mapping, since the
addresses referring to virtqueues are dma addresses.

We create the 1:1 MR in mlx5_vdpa_dev_add() only in case firmware
supports the general capability umem_uid_0. The reason for that is that
1:1 MRs must be created with uid == 0 while virtqueue objects can be
created with uid == 0 only when the firmware capability is on.

If the set_map() callback is called with new translations provided
through iotlb, the driver will destroy the 1:1 MR and create a regular
one.

Signed-off-by: Eli Cohen <elic@xxxxxxxxxx>
---
   drivers/vdpa/mlx5/core/mlx5_vdpa.h |  1 +
   drivers/vdpa/mlx5/core/mr.c        | 81 ++++++++++++++++++++++++------
   drivers/vdpa/mlx5/net/mlx5_vnet.c  | 13 ++++-
   3 files changed, 80 insertions(+), 15 deletions(-)

diff --git a/drivers/vdpa/mlx5/core/mlx5_vdpa.h b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
index b6cc53ba980c..09a16a3d1b2a 100644
--- a/drivers/vdpa/mlx5/core/mlx5_vdpa.h
+++ b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
@@ -35,6 +35,7 @@ struct mlx5_vdpa_mr {
   	/* serialize mkey creation and destruction */
   	struct mutex mkey_mtx;
+	bool user_mr;
   };
   struct mlx5_vdpa_resources {
diff --git a/drivers/vdpa/mlx5/core/mr.c b/drivers/vdpa/mlx5/core/mr.c
index 800cfd1967ad..020c0ce4d203 100644
--- a/drivers/vdpa/mlx5/core/mr.c
+++ b/drivers/vdpa/mlx5/core/mr.c
@@ -360,7 +360,7 @@ static int add_direct_chain(struct mlx5_vdpa_dev *mvdev, u64 start, u64 size, u8
    * indirect memory key that provides access to the enitre address space given
    * by iotlb.
    */
-static int _mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb *iotlb)
+static int create_user_mr(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb *iotlb)
   {
   	struct mlx5_vdpa_mr *mr = &mvdev->mr;
   	struct mlx5_vdpa_direct_mr *dmr;
@@ -374,9 +374,6 @@ static int _mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb
   	int err = 0;
   	int nnuls;
-	if (mr->initialized)
-		return 0;
-
   	INIT_LIST_HEAD(&mr->head);
   	for (map = vhost_iotlb_itree_first(iotlb, start, last); map;
   	     map = vhost_iotlb_itree_next(map, start, last)) {
@@ -414,7 +411,7 @@ static int _mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb
   	if (err)
   		goto err_chain;
-	mr->initialized = true;
+	mr->user_mr = true;
   	return 0;
   err_chain:
@@ -426,33 +423,89 @@ static int _mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb
   	return err;
   }
-int mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb *iotlb)
+static int create_dma_mr(struct mlx5_vdpa_dev *mvdev, struct mlx5_vdpa_mr *mr)
+{
+	int inlen = MLX5_ST_SZ_BYTES(create_mkey_in);
+	void *mkc;
+	u32 *in;
+	int err;
+
+	in = kzalloc(inlen, GFP_KERNEL);
+	if (!in)
+		return -ENOMEM;
+
+	mkc = MLX5_ADDR_OF(create_mkey_in, in, memory_key_mkey_entry);
+
+	MLX5_SET(mkc, mkc, access_mode_1_0, MLX5_MKC_ACCESS_MODE_PA);
+	MLX5_SET(mkc, mkc, length64, 1);
+	MLX5_SET(mkc, mkc, lw, 1);
+	MLX5_SET(mkc, mkc, lr, 1);
+	MLX5_SET(mkc, mkc, pd, mvdev->res.pdn);
+	MLX5_SET(mkc, mkc, qpn, 0xffffff);
+
+	err = mlx5_vdpa_create_mkey(mvdev, &mr->mkey, in, inlen);
+	kfree(in);
+	return err;
+}
+
+static void destroy_dma_mr(struct mlx5_vdpa_dev *mvdev, struct mlx5_vdpa_mr *mr)
+{
+	mlx5_vdpa_destroy_mkey(mvdev, &mr->mkey);
+}
+
+static int _mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb *iotlb)
   {
   	struct mlx5_vdpa_mr *mr = &mvdev->mr;
   	int err;
-	mutex_lock(&mr->mkey_mtx);
+	if (mr->initialized)
+		return 0;
+
+	if (iotlb)
+		err = create_user_mr(mvdev, iotlb);
+	else
+		err = create_dma_mr(mvdev, mr);

Do we need to set user_mr to false here?
I think the right place to do this should be inside create_dma_mr(), the
same as we set it true in ().


Fine.



+
+	mr->initialized = true;
+	return err;
+}
+
+int mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev, struct vhost_iotlb *iotlb)
+{
+	int err;
+
+	mutex_lock(&mvdev->mr.mkey_mtx);
   	err = _mlx5_vdpa_create_mr(mvdev, iotlb);
-	mutex_unlock(&mr->mkey_mtx);
+	mutex_unlock(&mvdev->mr.mkey_mtx);
   	return err;
   }
-void mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev)
+static void destroy_user_mr(struct mlx5_vdpa_dev *mvdev, struct mlx5_vdpa_mr *mr)
   {
-	struct mlx5_vdpa_mr *mr = &mvdev->mr;
   	struct mlx5_vdpa_direct_mr *dmr;
   	struct mlx5_vdpa_direct_mr *n;
-	mutex_lock(&mr->mkey_mtx);
-	if (!mr->initialized)
-		goto out;
-
   	destroy_indirect_key(mvdev, mr);
   	list_for_each_entry_safe_reverse(dmr, n, &mr->head, list) {
   		list_del_init(&dmr->list);
   		unmap_direct_mr(mvdev, dmr);
   		kfree(dmr);
   	}
+}
+
+void mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev)
+{
+	struct mlx5_vdpa_mr *mr = &mvdev->mr;
+
+	mutex_lock(&mr->mkey_mtx);
+	if (!mr->initialized)
+		goto out;
+
+	if (mr->user_mr)
+		destroy_user_mr(mvdev, mr);
+	else
+		destroy_dma_mr(mvdev, mr);
+
   	memset(mr, 0, sizeof(*mr));
   	mr->initialized = false;
   out:
diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index fdf3e74bffbd..f16756661c19 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -1780,6 +1780,8 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
   		ndev->mvdev.status = 0;
   		ndev->mvdev.mlx_features = 0;
   		++mvdev->generation;
+		if (MLX5_CAP_GEN(mvdev->mdev, umem_uid_0))
+			mlx5_vdpa_create_mr(mvdev, NULL);

I wonder if it's possible/worth to avoid the destroy and re-create of dma MR
here. (In the case of it has been used by us).
If it is a user MR, you must destroy it since it is useless. If it's
DMA MR, you might be able to do it but since the DMA MR's are
lightweight, I don't think it's worth it.


Yes, I agree.

Thanks



Thanks


   		return;
   	}
@@ -1859,6 +1861,7 @@ static void mlx5_vdpa_free(struct vdpa_device *vdev)
   	ndev = to_mlx5_vdpa_ndev(mvdev);
   	free_resources(ndev);
+	mlx5_vdpa_destroy_mr(mvdev);
   	mlx5_vdpa_free_resources(&ndev->mvdev);
   	mutex_destroy(&ndev->reslock);
   }
@@ -2023,9 +2026,15 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name)
   	if (err)
   		goto err_mtu;
+	if (MLX5_CAP_GEN(mvdev->mdev, umem_uid_0)) {
+		err = mlx5_vdpa_create_mr(mvdev, NULL);
+		if (err)
+			goto err_res;
+	}
+
   	err = alloc_resources(ndev);
   	if (err)
-		goto err_res;
+		goto err_mr;
   	mvdev->vdev.mdev = &mgtdev->mgtdev;
   	err = _vdpa_register_device(&mvdev->vdev, 2 * mlx5_vdpa_max_qps(max_vqs));
@@ -2037,6 +2046,8 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name)
   err_reg:
   	free_resources(ndev);
+err_mr:
+	mlx5_vdpa_destroy_mr(mvdev);
   err_res:
   	mlx5_vdpa_free_resources(&ndev->mvdev);
   err_mtu:

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