Re: [Qemu-devel] [PATCH 1/2] qdev: add HotplugHandler->post_plug() callback

[Paolo Bonzini]

On 10/07/2018 17:50, Stefan Hajnoczi wrote:
> The ->pre_plug() callback is invoked before the device is realized.  The
> ->plug() callback is invoked when the device is being realized but
> before it is reset.
> 
> This patch adds a ->post_plug() callback which is invoked after the
> device has been reset.  This callback is needed by HotplugHandlers that
> need to wait until after ->reset().
> 
> Signed-off-by: Stefan Hajnoczi <address@hidden>

Thanks Stefan.  I looked a bit at the code last week, and it seemed to
me that pretty much all "plug" callbacks should be split into a
"pre_plug" (check) and a "post_plug" (commit).  So the patch is okay,
but please remove the Error** argument of post_plug, because all the
checks should have happened already (there is none in the case of
virtio-scsi).

Thanks,

Paolo

> ---
>  include/hw/hotplug.h | 12 ++++++++++++
>  hw/core/hotplug.c    | 11 +++++++++++
>  hw/core/qdev.c       |  7 +++++++
>  3 files changed, 30 insertions(+)
> 
> diff --git a/include/hw/hotplug.h b/include/hw/hotplug.h
> index 1a0516a479..1e8b1053b6 100644
> --- a/include/hw/hotplug.h
> +++ b/include/hw/hotplug.h
> @@ -47,6 +47,8 @@ typedef void (*hotplug_fn)(HotplugHandler *plug_handler,
>   * @parent: Opaque parent interface.
>   * @pre_plug: pre plug callback called at start of device.realize(true)
>   * @plug: plug callback called at end of device.realize(true).
> + * @post_plug: post plug callback called after device.realize(true) and 
> device
> + *             reset
>   * @unplug_request: unplug request callback.
>   *                  Used as a means to initiate device unplug for devices 
> that
>   *                  require asynchronous unplug handling.
> @@ -61,6 +63,7 @@ typedef struct HotplugHandlerClass {
>      /* <public> */
>      hotplug_fn pre_plug;
>      hotplug_fn plug;
> +    hotplug_fn post_plug;
>      hotplug_fn unplug_request;
>      hotplug_fn unplug;
>  } HotplugHandlerClass;
> @@ -83,6 +86,15 @@ void hotplug_handler_pre_plug(HotplugHandler *plug_handler,
>                                DeviceState *plugged_dev,
>                                Error **errp);
>  
> +/**
> + * hotplug_handler_post_plug:
> + *
> + * Call #HotplugHandlerClass.post_plug callback of @plug_handler.
> + */
> +void hotplug_handler_post_plug(HotplugHandler *plug_handler,
> +                               DeviceState *plugged_dev,
> +                               Error **errp);
> +
>  /**
>   * hotplug_handler_unplug_request:
>   *
> diff --git a/hw/core/hotplug.c b/hw/core/hotplug.c
> index 17ac986685..ab34c19461 100644
> --- a/hw/core/hotplug.c
> +++ b/hw/core/hotplug.c
> @@ -35,6 +35,17 @@ void hotplug_handler_plug(HotplugHandler *plug_handler,
>      }
>  }
>  
> +void hotplug_handler_post_plug(HotplugHandler *plug_handler,
> +                               DeviceState *plugged_dev,
> +                               Error **errp)
> +{
> +    HotplugHandlerClass *hdc = HOTPLUG_HANDLER_GET_CLASS(plug_handler);
> +
> +    if (hdc->post_plug) {
> +        hdc->post_plug(plug_handler, plugged_dev, errp);
> +    }
> +}
> +
>  void hotplug_handler_unplug_request(HotplugHandler *plug_handler,
>                                      DeviceState *plugged_dev,
>                                      Error **errp)
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index cf0db4b6da..78c0e031ff 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -865,6 +865,13 @@ static void device_set_realized(Object *obj, bool value, 
> Error **errp)
>          }
>          if (dev->hotplugged) {
>              device_reset(dev);
> +
> +            if (hotplug_ctrl) {
> +                hotplug_handler_post_plug(hotplug_ctrl, dev, &local_err);
> +                if (local_err != NULL) {
> +                    goto child_realize_fail;
> +                }
> +            }
>          }
>          dev->pending_deleted_event = false;
>      } else if (!value && dev->realized) {
>