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Subject: Re: [PATCH v1] vdpa/mlx5: Add support for running with virtio_vdpa
To:     Eli Cohen <elic@nvidia.com>
Cc:     mst@redhat.com, virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
References: <20210531160428.31454-1-elic@nvidia.com>
 <117f8549-85c5-6603-c941-77c63b596bdd@redhat.com>
 <20210601034018.GA203469@mtl-vdi-166.wap.labs.mlnx>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <cd1aee86-86df-b7df-e6da-5402f9525ce5@redhat.com>
Date:   Tue, 1 Jun 2021 13:00:05 +0800
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在 2021/6/1 上午11:40, Eli Cohen 写道:
> On Tue, Jun 01, 2021 at 10:09:45AM +0800, Jason Wang wrote:
>> 在 2021/6/1 上午12:04, 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@nvidia.com>
>>> ---
>>> v0 --> v1:
>>>     1. Clear user_mr after successful creation of DMA MR
>>>     2. Check return code of mlx5_vdpa_create_mr() and emit warning if
>>>        failed.
>>>
>>>    drivers/vdpa/mlx5/core/mlx5_vdpa.h |  1 +
>>>    drivers/vdpa/mlx5/core/mr.c        | 84 +++++++++++++++++++++++++-----
>>>    drivers/vdpa/mlx5/net/mlx5_vnet.c  | 15 +++++-
>>>    3 files changed, 85 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..3c6c1d846f5e 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 +423,92 @@ 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);
>>> +	if (!err)
>>> +		mr->user_mr = false;
>>
>> Rethink about this. I wonder this is correct when we fail to create memory
>> key.
>>
>> In this case, user_mr is true but user_mr is already destroyed. Can this
>> lead double free for user mr?
> mr->user_mr is a binary flag and its sole purpose is to tell the flavour
> of the MR but is valid only when mr->initialized is true. MR won't be
> freed if mr->initialized is false.


So we have:

static int _mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev, struct 
vhost_iotlb *iotlb)
{
         struct mlx5_vdpa_mr *mr = &mvdev->mr;
         int err;

         if (mr->initialized)
                 return 0;

         if (iotlb)
                 err = create_user_mr(mvdev, iotlb);
         else
                 err = create_dma_mr(mvdev, mr);

         mr->initialized = true;
         return err;
}

It looks to me we need to check err before set mr->initialized.

Thanks


>
>> Thanks
>>
>>
>>> +
>>> +	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);
>>> +
>>> +	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..02a05492204c 100644
>>> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>> @@ -1780,6 +1780,10 @@ 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)) {
>>> +			if (mlx5_vdpa_create_mr(mvdev, NULL))
>>> +				mlx5_vdpa_warn(mvdev, "create MR failed\n");
>>> +		}
>>>    		return;
>>>    	}
>>> @@ -1859,6 +1863,7 @@ 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 +2028,15 @@ 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 +2048,8 @@ 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: