linux-kernel - Re: [PATCH RESEND] vdpa/mlx5: Allow CVQ size changes

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Date: Thu, 15 Feb 2024 19:18:50 +0100
From: Dragos Tatulea <dtatulea@...dia.com>
To: Jonah Palmer <jonah.palmer@...cle.com>
Cc: mst@...hat.com, jasowang@...hat.com, xuanzhuo@...ux.alibaba.com, 
	eperezma@...hat.com, si-wei.liu@...cle.com, virtualization@...ts.linux-foundation.org, 
	boris.ostrovsky@...cle.com, leiyang@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND] vdpa/mlx5: Allow CVQ size changes

On 02/15, Jonah Palmer wrote:
> The MLX driver was not updating its control virtqueue size at set_vq_num
> and instead always initialized to MLX5_CVQ_MAX_ENT (16) at
> setup_cvq_vring.
> 
> Qemu would try to set the size to 64 by default, however, because the
> CVQ size always was initialized to 16, an error would be thrown when
> sending >16 control messages (as used-ring entry 17 is initialized to 0).
> For example, starting a guest with x-svq=on and then executing the
> following command would produce the error below:
> 
>  # for i in {1..20}; do ifconfig eth0 hw ether XX:xx:XX:xx:XX:XX; done
> 
>  qemu-system-x86_64: Insufficient written data (0)
>  [  435.331223] virtio_net virtio0: Failed to set mac address by vq command.
>  SIOCSIFHWADDR: Invalid argument
> 
> Signed-off-by: Jonah Palmer <jonah.palmer@...cle.com>

Thanks for the patch Jonah!
> ---
>  drivers/vdpa/mlx5/net/mlx5_vnet.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 778821bab7d9..c74de1fe6a94 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -2276,9 +2276,15 @@ static void mlx5_vdpa_set_vq_num(struct vdpa_device *vdev, u16 idx, u32 num)
>  	struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
>  	struct mlx5_vdpa_virtqueue *mvq;
>  
> -	if (!is_index_valid(mvdev, idx) || is_ctrl_vq_idx(mvdev, idx))
> +	if (!is_index_valid(mvdev, idx))
>  		return;
>  
> +        if (is_ctrl_vq_idx(mvdev, idx)) {
> +                struct mlx5_control_vq *cvq = &mvdev->cvq;
Nit: add a space between variable declarations and usage.

> +                cvq->vring.vring.num = num;
> +                return;
> +        }
> +
>  	mvq = &ndev->vqs[idx];
>  	mvq->num_ent = num;
>  }
> @@ -2963,7 +2969,7 @@ static int setup_cvq_vring(struct mlx5_vdpa_dev *mvdev)
>  		u16 idx = cvq->vring.last_avail_idx;
>  
>  		err = vringh_init_iotlb(&cvq->vring, mvdev->actual_features,
> -					MLX5_CVQ_MAX_ENT, false,
> +					cvq->vring.vring.num, false,
>  					(struct vring_desc *)(uintptr_t)cvq->desc_addr,
>  					(struct vring_avail *)(uintptr_t)cvq->driver_addr,
>  					(struct vring_used *)(uintptr_t)cvq->device_addr);

Besides the nit:

Acked-by: Dragos Tatulea <dtatulea@...dia.com>

> -- 
> 2.39.3
>