netdev - Re: [RFC v2 3/4] vduse: update the vq

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Date: Tue, 12 Sep 2023 15:39:08 +0800
From: Jason Wang <jasowang@...hat.com>
To: Cindy Lu <lulu@...hat.com>
Cc: mst@...hat.com, maxime.coquelin@...hat.com, xieyongji@...edance.com, 
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org, 
	stable@...r.kernel.org
Subject: Re: [RFC v2 3/4] vduse: update the vq_info in ioctl

On Tue, Sep 12, 2023 at 11:00 AM Cindy Lu <lulu@...hat.com> wrote:
>
> In VDUSE_VQ_GET_INFO, the driver will sync the last_avail_idx
> with reconnect info, After mapping the reconnect pages to userspace
> The userspace App will update the reconnect_time in
> struct vhost_reconnect_vring, If this is not 0 then it means this
> vq is reconnected and will update the last_avail_idx
>
> Signed-off-by: Cindy Lu <lulu@...hat.com>
> ---
>  drivers/vdpa/vdpa_user/vduse_dev.c | 13 +++++++++++++
>  include/uapi/linux/vduse.h         |  6 ++++++
>  2 files changed, 19 insertions(+)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index 2c69f4004a6e..680b23dbdde2 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -1221,6 +1221,8 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
>                 struct vduse_vq_info vq_info;
>                 struct vduse_virtqueue *vq;
>                 u32 index;
> +               struct vdpa_reconnect_info *area;
> +               struct vhost_reconnect_vring *vq_reconnect;
>
>                 ret = -EFAULT;
>                 if (copy_from_user(&vq_info, argp, sizeof(vq_info)))
> @@ -1252,6 +1254,17 @@ static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
>
>                 vq_info.ready = vq->ready;
>
> +               area = &vq->reconnect_info;
> +
> +               vq_reconnect = (struct vhost_reconnect_vring *)area->vaddr;
> +               /*check if the vq is reconnect, if yes then update the last_avail_idx*/
> +               if ((vq_reconnect->last_avail_idx !=
> +                    vq_info.split.avail_index) &&
> +                   (vq_reconnect->reconnect_time != 0)) {
> +                       vq_info.split.avail_index =
> +                               vq_reconnect->last_avail_idx;
> +               }
> +
>                 ret = -EFAULT;
>                 if (copy_to_user(argp, &vq_info, sizeof(vq_info)))
>                         break;
> diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h
> index 11bd48c72c6c..d585425803fd 100644
> --- a/include/uapi/linux/vduse.h
> +++ b/include/uapi/linux/vduse.h
> @@ -350,4 +350,10 @@ struct vduse_dev_response {
>         };
>  };
>
> +struct vhost_reconnect_vring {
> +       __u16 reconnect_time;
> +       __u16 last_avail_idx;
> +       _Bool avail_wrap_counter;

Please add a comment for each field.

And I never saw _Bool is used in uapi before, maybe it's better to
pack it with last_avail_idx into a __u32.

Btw, do we need to track inflight descriptors as well?

Thanks

> +};
> +
>  #endif /* _UAPI_VDUSE_H_ */
> --
> 2.34.3
>