Re: [Qemu-devel] [PATCH 3/5] PXB: convert to realize()

[Marcel Apfelbaum <marcel@redhat.com>]

On 12/20/2015 12:48 PM, Cao jin wrote:
> Hi,
>
> On 12/20/2015 06:22 PM, Marcel Apfelbaum wrote:
>>
>> Hi,
>>
>> On 12/18/2015 01:03 PM, Cao jin wrote:
>>> Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
>>> ---
>>>   hw/pci-bridge/pci_expander_bridge.c | 24 ++++++++++++++----------
>>>   1 file changed, 14 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/hw/pci-bridge/pci_expander_bridge.c
>>> b/hw/pci-bridge/pci_expander_bridge.c
>>> index 57f8a37..cc975f6 100644
>>> --- a/hw/pci-bridge/pci_expander_bridge.c
>>> +++ b/hw/pci-bridge/pci_expander_bridge.c
>>> @@ -145,19 +145,19 @@ static const TypeInfo pxb_host_info = {
>>>    * Returns 0 on successs, -1 if i440fx host was not
>>>    * found or the bus number is already in use.
>>>    */
>>> -static int pxb_register_bus(PCIDevice *dev, PCIBus *pxb_bus)
>>> +static int pxb_register_bus(PCIDevice *dev, PCIBus *pxb_bus, Error
>>> **errp)
>>
>> If you add an err parameter, maybe the function should return void.
>>
>
> Ok, will modify it in V2. Actually, both style are fine with me:)
>
>>
>>>   {
>>>       PCIBus *bus = dev->bus;
>>>       int pxb_bus_num = pci_bus_num(pxb_bus);
>>>
>>>       if (bus->parent_dev) {
>>> -        error_report("PXB devices can be attached only to root bus.");
>>> +        error_setg(errp, "PXB devices can be attached only to root
>>> bus.");
>>>           return -1;
>>>       }
>>>
>>>       QLIST_FOREACH(bus, &bus->child, sibling) {
>>>           if (pci_bus_num(bus) == pxb_bus_num) {
>>> -            error_report("Bus %d is already in use.", pxb_bus_num);
>>> +            error_setg(errp, "Bus %d is already in use.", pxb_bus_num);
>>>               return -1;
>>>           }
>>>       }
>>> @@ -193,7 +193,7 @@ static gint pxb_compare(gconstpointer a,
>>> gconstpointer b)
>>>              0;
>>>   }
>>>
>>> -static int pxb_dev_initfn(PCIDevice *dev)
>>> +static void pxb_dev_realize(PCIDevice *dev, Error **errp)
>>>   {
>>>       PXBDev *pxb = PXB_DEV(dev);
>>>       DeviceState *ds, *bds;
>>> @@ -202,8 +202,8 @@ static int pxb_dev_initfn(PCIDevice *dev)
>>>
>>>       if (pxb->numa_node != NUMA_NODE_UNASSIGNED &&
>>>           pxb->numa_node >= nb_numa_nodes) {
>>> -        error_report("Illegal numa node %d.", pxb->numa_node);
>>> -        return -EINVAL;
>>> +        error_setg(errp, "Illegal numa node %d.", pxb->numa_node);
>>> +        return;
>>>       }
>>>
>>>       if (dev->qdev.id && *dev->qdev.id) {
>>> @@ -225,8 +225,8 @@ static int pxb_dev_initfn(PCIDevice *dev)
>>>
>>>       PCI_HOST_BRIDGE(ds)->bus = bus;
>>>
>>> -    if (pxb_register_bus(dev, bus)) {
>>> -        return -EINVAL;
>>> +    if (pxb_register_bus(dev, bus, errp)) {
>>> +        goto err_register_bus;
>>>       }
>>>
>>>       qdev_init_nofail(ds);
>>> @@ -237,7 +237,11 @@ static int pxb_dev_initfn(PCIDevice *dev)
>>>       pci_config_set_class(dev->config, PCI_CLASS_BRIDGE_HOST);
>>>
>>>       pxb_dev_list = g_list_insert_sorted(pxb_dev_list, pxb,
>>> pxb_compare);
>>> -    return 0;
>>> +
>>> +err_register_bus:
>>> +    object_unref(OBJECT(ds));
>>> +    object_unref(OBJECT(bds));
>>> +    object_unref(OBJECT(bus));
>>
>>
>> The order should be in the reverse order of creation:
>>      bds, bus, ds
>>
>
> Ok, I can do that. But it seems the order here doesn`t matter? Is there dependency among these three?

Yes, there is a dependency:
At first the pxb host (ds) is created, then the bus (bus) is created as host's child (see pci_bus_new)
and in the end a pci bridge (bds) is attached to the bus (see qdev_create).

By the way, indeed you should call object_unparent at least for the pxb_host(ds), but you may want to
check the others parent relationship as well.

>
>>
>>>   }
>>>
>>>   static void pxb_dev_exitfn(PCIDevice *pci_dev)
>>> @@ -259,7 +263,7 @@ static void pxb_dev_class_init(ObjectClass *klass,
>>> void *data)
>>>       DeviceClass *dc = DEVICE_CLASS(klass);
>>>       PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
>>>
>>> -    k->init = pxb_dev_initfn;
>>> +    k->realize = pxb_dev_realize;
>>>       k->exit = pxb_dev_exitfn;
>>
>> If init is converted to realize, maybe the exit should be converted to
>> unrealize?
>>
>
> Yup, I agree with you from the point that the names should be antonym. But it seems there is no PCIDeviceClass.unrealize:(

You are right. The pci_qdev_unrealize ultimately calls exit. But the same goes for init, pci_qdev_realize calls for pc->realize.
This is the reason I chose to use init/exit instead of the strange realize/exit.

But since the intention is to get rid of init, I am not against it.

>
> And I am also not aware why there is no comment for .exit while there is for .init. It is appreciated if somebody could tell me the history O:-)

I'll add Markus, Andreas and Michael (the PCI maintainer), maybe they have a better insight to this.

On the other hand you should continue with the patch and leave the "unrealize" until we'll know more :)

Thanks,
Marcel

>
>>
>> Thanks,
>> Marcel
>>
>>>       k->vendor_id = PCI_VENDOR_ID_REDHAT;
>>>       k->device_id = PCI_DEVICE_ID_REDHAT_PXB;
>>>
>>
>>
>>
>> .
>>
>