Re: [PATCH v3 5/5] vhost-user-scsi: start vhost when guest kicks

[Markus Armbruster <armbru@redhat.com>]

Li Feng <fengli@smartx.com> writes:

> Let's keep the same behavior as vhost-user-blk.
>
> Some old guests kick virtqueue before setting VIRTIO_CONFIG_S_DRIVER_OK.
>
> Signed-off-by: Li Feng <fengli@smartx.com>
> ---
>  hw/scsi/vhost-user-scsi.c | 48 +++++++++++++++++++++++++++++++++++----
>  1 file changed, 44 insertions(+), 4 deletions(-)
>
> diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c
> index 5bf012461b..a7fa8e8df2 100644
> --- a/hw/scsi/vhost-user-scsi.c
> +++ b/hw/scsi/vhost-user-scsi.c
> @@ -113,8 +113,48 @@ static void vhost_user_scsi_reset(VirtIODevice *vdev)
>      }
>  }
>  
> -static void vhost_dummy_handle_output(VirtIODevice *vdev, VirtQueue *vq)
> +static void vhost_user_scsi_handle_output(VirtIODevice *vdev, VirtQueue *vq)
>  {
> +    VHostUserSCSI *s = (VHostUserSCSI *)vdev;
> +    DeviceState *dev = &s->parent_obj.parent_obj.parent_obj.parent_obj;
> +    VHostSCSICommon *vsc = VHOST_SCSI_COMMON(s);
> +    VirtIOSCSICommon *vs = VIRTIO_SCSI_COMMON(dev);
> +
> +    Error *local_err = NULL;
> +    int i, ret;
> +
> +    if (!vdev->start_on_kick) {
> +        return;
> +    }
> +
> +    if (!s->connected) {
> +        return;
> +    }
> +
> +    if (vhost_dev_is_started(&vsc->dev)) {
> +        return;
> +    }
> +
> +    /*
> +     * Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
> +     * vhost here instead of waiting for .set_status().
> +     */
> +    ret = vhost_user_scsi_start(s);
> +    if (ret < 0) {
> +        error_reportf_err(local_err, "vhost-user-scsi: vhost start failed: ");

Crashes, since @local_err is null.  Please test your error paths.

Obvious fix: drop this call.

> +        qemu_chr_fe_disconnect(&vs->conf.chardev);
> +        return;
> +    }
> +
> +    /* Kick right away to begin processing requests already in vring */
> +    for (i = 0; i < vsc->dev.nvqs; i++) {
> +        VirtQueue *kick_vq = virtio_get_queue(vdev, i);
> +
> +        if (!virtio_queue_get_desc_addr(vdev, i)) {
> +            continue;
> +        }
> +        event_notifier_set(virtio_queue_get_host_notifier(kick_vq));
> +    }
>  }
>  
>  static int vhost_user_scsi_connect(DeviceState *dev, Error **errp)
> @@ -243,9 +283,9 @@ static void vhost_user_scsi_realize(DeviceState *dev, Error **errp)
>          return;
>      }
>  
> -    virtio_scsi_common_realize(dev, vhost_dummy_handle_output,
> -                               vhost_dummy_handle_output,
> -                               vhost_dummy_handle_output, &err);
> +    virtio_scsi_common_realize(dev, vhost_user_scsi_handle_output,
> +                               vhost_user_scsi_handle_output,
> +                               vhost_user_scsi_handle_output, &err);
>      if (err != NULL) {
>          error_propagate(errp, err);
>          return;