Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH 3/3] mlx5_vdpa: defer clear_virtqueues to until DRIVER_OK
To:     Si-Wei Liu <si-wei.liu@oracle.com>, mst@redhat.com, elic@nvidia.com
Cc:     linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org
References: <1612614564-4220-1-git-send-email-si-wei.liu@oracle.com>
 <1612614564-4220-3-git-send-email-si-wei.liu@oracle.com>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <17374b6e-83c5-29c8-de28-60e06f4ce6ca@redhat.com>
Date:   Mon, 8 Feb 2021 12:38:15 +0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <1612614564-4220-3-git-send-email-si-wei.liu@oracle.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-US
Precedence: bulk


On 2021/2/6 下午8:29, Si-Wei Liu wrote:
> While virtq is stopped,  get_vq_state() is supposed to
> be  called to  get  sync'ed  with  the latest internal
> avail_index from device. The saved avail_index is used
> to restate  the virtq  once device is started.  Commit
> b35ccebe3ef7 introduced the clear_virtqueues() routine
> to  reset  the saved  avail_index,  however, the index
> gets cleared a bit earlier before get_vq_state() tries
> to read it. This would cause consistency problems when
> virtq is restarted, e.g. through a series of link down
> and link up events. We  could  defer  the  clearing of
> avail_index  to  until  the  device  is to be started,
> i.e. until  VIRTIO_CONFIG_S_DRIVER_OK  is set again in
> set_status().
>
> Fixes: b35ccebe3ef7 ("vdpa/mlx5: Restore the hardware used index after change map")
> Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>


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


> ---
>   drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index aa6f8cd..444ab58 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -1785,7 +1785,6 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
>   	if (!status) {
>   		mlx5_vdpa_info(mvdev, "performing device reset\n");
>   		teardown_driver(ndev);
> -		clear_virtqueues(ndev);
>   		mlx5_vdpa_destroy_mr(&ndev->mvdev);
>   		ndev->mvdev.status = 0;
>   		++mvdev->generation;
> @@ -1794,6 +1793,7 @@ static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
>   
>   	if ((status ^ ndev->mvdev.status) & VIRTIO_CONFIG_S_DRIVER_OK) {
>   		if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
> +			clear_virtqueues(ndev);
>   			err = setup_driver(ndev);
>   			if (err) {
>   				mlx5_vdpa_warn(mvdev, "failed to setup driver\n");