Re: [Qemu-devel] [PATCH 04/11] qdev: add to BusState "hotplug-handler" link

[Igor Mammedov <imammedo@redhat.com>]

On Sat, 14 Dec 2013 17:05:57 +1000
Peter Crosthwaite <peter.crosthwaite@xilinx.com> wrote:

> On Fri, Dec 13, 2013 at 10:44 PM, Igor Mammedov <imammedo@redhat.com> wrote:
> > It will allow to reuse field with different BUSes, reducing code duplication.
> > Field is intended fot replacing 'hotplug_qdev' field in PCIBus and also
> > will allow to avoid adding equivalent field to DimmBus with possiblitity
> > to refactor other BUSes to use it instead of custom field.
> > In addition once all users of allow_hotplug field are converted to new
> > API, link could replace allow_hotplug in qdev hotplug code.
> >
> > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > ---
> >  hw/core/qdev.c         | 4 ++++
> >  include/hw/qdev-core.h | 5 +++++
> >  2 files changed, 9 insertions(+)
> >
> > diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> > index e374a93..25c2d2c 100644
> > --- a/hw/core/qdev.c
> > +++ b/hw/core/qdev.c
> > @@ -32,6 +32,7 @@
> >  #include "qapi/visitor.h"
> >  #include "qapi/qmp/qjson.h"
> >  #include "monitor/monitor.h"
> > +#include "hw/hotplug.h"
> >
> >  int qdev_hotplug = 0;
> >  static bool qdev_hot_added = false;
> > @@ -868,6 +869,9 @@ static void qbus_initfn(Object *obj)
> >      BusState *bus = BUS(obj);
> >
> >      QTAILQ_INIT(&bus->children);
> > +    object_property_add_link(obj, QDEV_HOTPLUG_HANDLER_PROPERTY,
> > +                             TYPE_HOTPLUG_HANDLER,
> > +                             (Object **)&bus->hotplug_handler, NULL);
> 
> I think failure of this is fatal. When the patches go through,
> probably want to &error_abort.
That's just another example of we don't care about error that
gave birth to &error_abort topic. But I think is a drawback if
error-less initfn. We have a lot of such usage without a way
to report error, that's why "we don't care about error" was
invented I guess.

But more to the point, bus could be created during hotplug, and
we do not want to abort guest, instead hotplug operation should fail.
In this case following setting of QDEV_HOTPLUG_HANDLER_PROPERTY
will fail if object_property_add_link() failed before.

> 
> >  }
> >
> >  static char *default_bus_get_fw_dev_path(DeviceState *dev)
> > diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> > index f2043a6..684a5da 100644
> > --- a/include/hw/qdev-core.h
> > +++ b/include/hw/qdev-core.h
> > @@ -8,6 +8,7 @@
> >  #include "qom/object.h"
> >  #include "hw/irq.h"
> >  #include "qapi/error.h"
> > +#include "hw/hotplug.h"
> >
> >  enum {
> >      DEV_NVECTORS_UNSPECIFIED = -1,
> > @@ -169,14 +170,18 @@ typedef struct BusChild {
> >      QTAILQ_ENTRY(BusChild) sibling;
> >  } BusChild;
> >
> > +#define QDEV_HOTPLUG_HANDLER_PROPERTY "hotplug-handler"
> > +
> >  /**
> >   * BusState:
> > + * @hotplug_device: link to a hotplug device associated with bus.
> >   */
> >  struct BusState {
> >      Object obj;
> >      DeviceState *parent;
> >      const char *name;
> >      int allow_hotplug;
> > +    HotplugHandler *hotplug_handler;
> >      int max_index;
> >      QTAILQ_HEAD(ChildrenHead, BusChild) children;
> >      QLIST_ENTRY(BusState) sibling;
> > --
> > 1.8.3.1
> >
> >