netdev - Re: [PATCH v2] vdpa/mlx5: Setup driver only if VIRTIO_CONFIG_S_DRIVER

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Date:   Tue, 13 Oct 2020 13:37:43 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Eli Cohen <elic@...dia.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>, Cindy Lu <lulu@...hat.com>,
        virtualization@...ts.linux-foundation.org,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v2] vdpa/mlx5: Setup driver only if
 VIRTIO_CONFIG_S_DRIVER_OK


On 2020/9/9 下午1:30, Eli Cohen wrote:
> On Tue, Sep 08, 2020 at 10:08:39PM -0400, Jason Wang wrote:
>>
>> ----- Original Message -----
>>> set_map() is used by mlx5 vdpa to create a memory region based on the
>>> address map passed by the iotlb argument. If we get successive calls, we
>>> will destroy the current memory region and build another one based on
>>> the new address mapping. We also need to setup the hardware resources
>>> since they depend on the memory region.
>>>
>>> If these calls happen before DRIVER_OK, It means that driver VQs may
>>> also not been setup and we may not create them yet. In this case we want
>>> to avoid setting up the other resources and defer this till we get
>>> DRIVER OK.
>>>
>>> Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices")
>>> Signed-off-by: Eli Cohen <elic@...dia.com>
>>> ---
>>> V1->V2: Improve changelog description
>>>
>>>   drivers/vdpa/mlx5/net/mlx5_vnet.c | 3 +++
>>>   1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>> b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>> index 9df69d5efe8c..c89cd48a0aab 100644
>>> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
>>> @@ -1645,6 +1645,9 @@ static int mlx5_vdpa_change_map(struct mlx5_vdpa_net
>>> *ndev, struct vhost_iotlb *
>>>   	if (err)
>>>   		goto err_mr;
>>>   
>>> +	if (!(ndev->mvdev.status & VIRTIO_CONFIG_S_DRIVER_OK))
>>> +		return 0;
>>> +
>> Is there any reason that we still need to do vq suspending and saving before?
>>
> Though suspend_vqs() and save_channels_info() will be called, they will
> not actually do any work because the mvq->initialized is false.
>
> Since we don't expect so many false map updates I think it makes sense
> to avoid logic around the calls suspend_vqs() and save_channels_info().


I see.

Acked-by: Jason Wang <jasowang@...hat.com>

Thanks


>
>> Thanks
>>
>>>   	restore_channels_info(ndev);
>>>   	err = setup_driver(ndev);
>>>   	if (err)
>>> --
>>> 2.26.0
>>>
>>>