linux-kernel - Re: [PATCH v1] vdpa/mlx5: Clear vq ready indication upon device reset

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Message-ID: <9ec6480d-3eee-c644-2a06-8a180aa9fb07@redhat.com>
Date:   Fri, 4 Jun 2021 10:34:29 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Eli Cohen <elic@...dia.com>, mst@...hat.com,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] vdpa/mlx5: Clear vq ready indication upon device reset


在 2021/6/3 下午4:10, Eli Cohen 写道:
> After device reset, the virtqueues are not ready so clear the ready
> field.
>
> Failing to do so can result in virtio_vdpa failing to load if the device
> was previously used by vhost_vdpa and the old values are ready.
> virtio_vdpa expects to find VQs in "not ready" state.
>
> Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices")
> Signed-off-by: Eli Cohen <elic@...dia.com>
> ---
> v0 --> v1:
>    Make sure clear of ready is done only in reset flow
>
>   drivers/vdpa/mlx5/net/mlx5_vnet.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 02a05492204c..eaeae67e0ff0 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -1766,6 +1766,14 @@ static void teardown_driver(struct mlx5_vdpa_net *ndev)
>   	mutex_unlock(&ndev->reslock);
>   }
>   
> +static void clear_vqs_ready(struct mlx5_vdpa_net *ndev)
> +{
> +	int i;
> +
> +	for (i = ndev->mvdev.max_vqs - 1; i >= 0; i--)
> +		ndev->vqs[i].ready = false;


The patch looks correct but I wonder the reason for the decreasing used 
in the loop.

Usually, it means it has some reason that must be done in that way.

Thanks


> +}
> +
>   static void mlx5_vdpa_set_status(struct vdpa_device *vdev, u8 status)
>   {
>   	struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> @@ -1776,6 +1784,7 @@ 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_vqs_ready(ndev);
>   		mlx5_vdpa_destroy_mr(&ndev->mvdev);
>   		ndev->mvdev.status = 0;
>   		ndev->mvdev.mlx_features = 0;