Re: [Qemu-devel] [PATCH v6 02/27] bootindex: add del_boot_device_path function

[Gonglei (Arei)]

> Subject: Re: [PATCH v6 02/27] bootindex: add del_boot_device_path function
> 
> On Thu, Sep 04, 2014 at 03:01:41AM +0000, Gonglei (Arei) wrote:
> > Hi,
> >
> > > From: Eduardo Habkost [mailto:address@hidden
> > > Sent: Thursday, September 04, 2014 2:13 AM
> > > Subject: Re: [PATCH v6 02/27] bootindex: add del_boot_device_path
> function
> > >
> > > On Wed, Sep 03, 2014 at 06:45:56AM +0000, Gonglei (Arei) wrote:
> > > [...]
> > > > > > 4. When we hotplug the virtio-net-pci device, only pass 
> > > > > > virtio-net-pci's
> > > pointer
> > > > > to
> > > > > > del_boot_device_path(). But virtio-net-pci != virtio-net-device, so 
> > > > > > I add
> a
> > > > > function
> > > > > > named is_same_fw_dev_path() to handle this situation.
> > > > >
> > > > > When hot-unplugging virtio-net-pci I'd expect we free both
> > > > > virtio-net-pci and virtio-net-device (and therefore call
> > > > > del_boot_device_path twice, once for each device).  Can you check
> that?
> > > > >
> > > > Yes, I can.
> > > >
> > > > The del_boot_device_path() is called only once, just for virtio-net-pci.
> > > > For its child, virtio-net-devcie's resource is cleaned by qbus->child
> unrealizing
> > > > process, will not call device_finalize().
> > >
> > > Then we need to fix this to make sure there's a corresponding
> > > del_boot_device_path() call (with the same pointer) to every
> > > add_boot_device_path() call, instead of adding a hack to
> > > del_boot_device_path().
> > >
> > Good idea. We can add functions named $device_finalize_bootindex(), such
> as:
> >
> > static void virtio_net_set_bootindex(Object *obj, Visitor *v, void *opaque,
> >                                      const char *name, Error
> **errp)
> > {
> >     VirtIONet *n = VIRTIO_NET(obj);
> >
> >     set_bootindex(&n->nic_conf, v, name, errp);
> >     add_boot_device_path(n->nic_conf.bootindex,
> >                          DEVICE(obj), "/address@hidden");
> > }
> >
> > static void virtio_net_finalize_bootindex(Object *obj, const char *name,
> >                                           void *opaque)
> > {
> >     del_boot_device_path(DEVICE(obj));
> > }
> > ...
> > object_property_add(obj, "bootindex", "int",
> >                         virtio_net_get_bootindex,
> >                         virtio_net_set_bootindex,
> >                         virtio_net_finalize_bootindex, dev, NULL);
> >
> > as the previous email, we lay add_boot_device_path() in
> $device_set_bootindex,
> > and lay del_boot_device_path() in $device_finalize_bootindex is a good idea
> IMO.
> 
> Whatever the approach we use, 

Hmm... we just call this function in device_finalize() as I have used.
My above explanation is wrong because of a virtio-net's bug. Thanks.

> can we have a wrapper to reduce code
> duplication? e.g. a:
>   void device_add_bootindex_property(DeviceState *dev, int32_t *field, const
> char *suffix)
> function.
> 
> Then instead of reimplementing set/get/finalize functions, device code
> could just call something like:
>   device_add_bootindex_property(dev, &n->nic_conf.bootindex,
>                                 "/address@hidden");
> 

This way we cannot attach our target that changing bootindex and take effect
during vm rebooting.

> --
> Eduardo

Best regards,
-Gonglei