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Subject: Re: [PATCH 2/2] vdpa/mlx5: Add support for running with virtio_vdpa
To:     Eli Cohen <elic@nvidia.com>, mst@redhat.com,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
References: <20210530075415.4644-1-elic@nvidia.com>
 <20210530075415.4644-3-elic@nvidia.com>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <9b130015-d116-7fb0-1b86-2604353a2283@redhat.com>
Date:   Mon, 31 May 2021 11:16:11 +0800
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?? 2021/5/30 ????3:54, Eli Cohen д??:
> 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@nvidia.com>
> ---
>   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?


> +
> +	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).

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: