Re: [PATCH] vhost-user-blk: reset the device if supported

[Stefan Hajnoczi]

On Fri, Jan 10, 2020 at 08:22:03PM +0800, Yang Zhong wrote:
> As the vhost-user-scsi did in f04724, if the vhost-user-blk backend
> supports the VHOST_USER_F_RESET_DEVICE protocol feature, then the
> device can be reset when requested.
> 
> If this feature is not supported, this reset will directly return.
> 
> Signed-off-by: Yang Zhong <address@hidden>
> ---
>  hw/block/vhost-user-blk.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
> index 63da9bb619..16ddc9b70c 100644
> --- a/hw/block/vhost-user-blk.c
> +++ b/hw/block/vhost-user-blk.c
> @@ -50,6 +50,10 @@ static const int user_feature_bits[] = {
>      VHOST_INVALID_FEATURE_BIT
>  };
>  
> +enum VhostUserProtocolFeature {
> +    VHOST_USER_PROTOCOL_F_RESET_DEVICE = 13,
> +};

vhost-user protocol constants should be defined in
hw/virtio/vhost-user.h and not duplicated in device implementations.

> +
>  static void vhost_user_blk_update_config(VirtIODevice *vdev, uint8_t *config)
>  {
>      VHostUserBlk *s = VHOST_USER_BLK(vdev);
> @@ -290,8 +294,23 @@ static void vhost_user_blk_handle_output(VirtIODevice 
> *vdev, VirtQueue *vq)
>  static void vhost_user_blk_reset(VirtIODevice *vdev)
>  {
>      VHostUserBlk *s = VHOST_USER_BLK(vdev);
> +    struct vhost_dev *dev = &s->dev;
>  
>      vhost_dev_free_inflight(s->inflight);
> +
> +    /*
> +     * Historically, reset was not implemented so only reset devices
> +     * that are expecting it.
> +     */
> +    if (!virtio_has_feature(dev->protocol_features,
> +                            VHOST_USER_PROTOCOL_F_RESET_DEVICE)) {
> +        return;
> +    }
> +
> +    if (dev->vhost_ops->vhost_reset_device) {
> +        dev->vhost_ops->vhost_reset_device(dev);
> +    }
> +
>  }

This should be a generic protocol feature that all vhost-user device
implementations benefit from.  Devices shouldn't have to explicitly
implement it over and over again.

Why isn't vhost_user_reset_device() called already?  Then it wouldn't be
necessary to modify vhost_user_blk_reset().

Stefan

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