linux-kernel - Re: [PATCH vhost 19/23] vdpa/mlx5: Use suspend/resume during VQP change

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Date: Wed, 19 Jun 2024 17:46:57 +0200
From: Eugenio Perez Martin <eperezma@...hat.com>
To: Dragos Tatulea <dtatulea@...dia.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, 
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Saeed Mahameed <saeedm@...dia.com>, 
	Leon Romanovsky <leon@...nel.org>, Tariq Toukan <tariqt@...dia.com>, Si-Wei Liu <si-wei.liu@...cle.com>, 
	virtualization@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	linux-rdma@...r.kernel.org, netdev@...r.kernel.org, 
	Cosmin Ratiu <cratiu@...dia.com>
Subject: Re: [PATCH vhost 19/23] vdpa/mlx5: Use suspend/resume during VQP change

On Mon, Jun 17, 2024 at 5:09 PM Dragos Tatulea <dtatulea@...dia.com> wrote:
>
> Resume a VQ if it is already created when the number of VQ pairs
> increases. This is done in preparation for VQ pre-creation which is
> coming in a later patch. It is necessary because calling setup_vq() on
> an already created VQ will return early and will not enable the queue.
>
> For symmetry, suspend a VQ instead of tearing it down when the number of
> VQ pairs decreases. But only if the resume operation is supported.
>
> Signed-off-by: Dragos Tatulea <dtatulea@...dia.com>
> Reviewed-by: Cosmin Ratiu <cratiu@...dia.com>

Acked-by: Eugenio Pérez <eperezma@...hat.com>

> ---
>  drivers/vdpa/mlx5/net/mlx5_vnet.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 0e1c1b7ff297..249b5afbe34a 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -2130,14 +2130,22 @@ static int change_num_qps(struct mlx5_vdpa_dev *mvdev, int newqps)
>                 if (err)
>                         return err;
>
> -               for (i = ndev->cur_num_vqs - 1; i >= 2 * newqps; i--)
> -                       teardown_vq(ndev, &ndev->vqs[i]);
> +               for (i = ndev->cur_num_vqs - 1; i >= 2 * newqps; i--) {
> +                       struct mlx5_vdpa_virtqueue *mvq = &ndev->vqs[i];
> +
> +                       if (is_resumable(ndev))
> +                               suspend_vq(ndev, mvq);
> +                       else
> +                               teardown_vq(ndev, mvq);
> +               }
>
>                 ndev->cur_num_vqs = 2 * newqps;
>         } else {
>                 ndev->cur_num_vqs = 2 * newqps;
>                 for (i = cur_qps * 2; i < 2 * newqps; i++) {
> -                       err = setup_vq(ndev, &ndev->vqs[i], true);
> +                       struct mlx5_vdpa_virtqueue *mvq = &ndev->vqs[i];
> +
> +                       err = mvq->initialized ? resume_vq(ndev, mvq) : setup_vq(ndev, mvq, true);
>                         if (err)
>                                 goto clean_added;
>                 }
>
> --
> 2.45.1
>