Re: [Qemu-devel] [PATCH RFC qom-next 4/4] pcie_port: Turn PCIEPort and PCIESlot into abstract QOM types

["Andreas Färber" <afaerber@suse.de>]

Am 21.07.2013 22:26, schrieb Michael S. Tsirkin:
> On Sun, Jul 21, 2013 at 04:09:04PM +0200, Andreas Färber wrote:
>> Signed-off-by: Andreas Färber <afaerber@suse.de>
>> ---
>>  hw/pci-bridge/ioh3420.c            | 23 ++++++++++-------------
>>  hw/pci-bridge/xio3130_downstream.c | 23 ++++++++++-------------
>>  hw/pci-bridge/xio3130_upstream.c   | 15 +++++++--------
>>  hw/pci/pcie_port.c                 | 22 ++++++++++++++++++++++
>>  include/hw/pci/pcie_port.h         | 14 ++++++++++++--
>>  5 files changed, 61 insertions(+), 36 deletions(-)
>>
>> diff --git a/hw/pci-bridge/ioh3420.c b/hw/pci-bridge/ioh3420.c
>> index 728f658..83db054 100644
>> --- a/hw/pci-bridge/ioh3420.c
>> +++ b/hw/pci-bridge/ioh3420.c
>> @@ -92,9 +92,8 @@ static void ioh3420_reset(DeviceState *qdev)
>>  
>>  static int ioh3420_initfn(PCIDevice *d)
>>  {
>> -    PCIBridge *br = PCI_BRIDGE(d);
>> -    PCIEPort *p = DO_UPCAST(PCIEPort, br, br);
>> -    PCIESlot *s = DO_UPCAST(PCIESlot, port, p);
>> +    PCIEPort *p = PCIE_PORT(d);
>> +    PCIESlot *s = PCIE_SLOT(d);
>>      int rc;
>>  
>>      rc = pci_bridge_initfn(d, TYPE_PCIE_BUS);
>> @@ -148,9 +147,7 @@ err_bridge:
>>  
>>  static void ioh3420_exitfn(PCIDevice *d)
>>  {
>> -    PCIBridge *br = PCI_BRIDGE(d);
>> -    PCIEPort *p = DO_UPCAST(PCIEPort, br, br);
>> -    PCIESlot *s = DO_UPCAST(PCIESlot, port, p);
>> +    PCIESlot *s = PCIE_SLOT(d);
>>  
>>      pcie_aer_exit(d);
>>      pcie_chassis_del_slot(s);
>> @@ -180,7 +177,7 @@ PCIESlot *ioh3420_init(PCIBus *bus, int devfn, bool multifunction,
>>      qdev_prop_set_uint16(qdev, "slot", slot);
>>      qdev_init_nofail(qdev);
>>  
>> -    return DO_UPCAST(PCIESlot, port, DO_UPCAST(PCIEPort, br, br));
>> +    return PCIE_SLOT(d);
>>  }
>>  
>>  static const VMStateDescription vmstate_ioh3420 = {
>> @@ -190,19 +187,19 @@ static const VMStateDescription vmstate_ioh3420 = {
>>      .minimum_version_id_old = 1,
>>      .post_load = pcie_cap_slot_post_load,
>>      .fields = (VMStateField[]) {
>> -        VMSTATE_PCIE_DEVICE(port.br.parent_obj, PCIESlot),
>> -        VMSTATE_STRUCT(port.br.parent_obj.exp.aer_log, PCIESlot, 0,
>> +        VMSTATE_PCIE_DEVICE(parent_obj, PCIBridge),
>> +        VMSTATE_STRUCT(exp.aer_log, PCIDevice, 0,
>>                         vmstate_pcie_aer_log, PCIEAERLog),
>>          VMSTATE_END_OF_LIST()
>>      }
>>  };
>>  
>>  static Property ioh3420_properties[] = {
>> -    DEFINE_PROP_UINT8("port", PCIESlot, port.port, 0),
>> +    DEFINE_PROP_UINT8("port", PCIEPort, port, 0),
>>      DEFINE_PROP_UINT8("chassis", PCIESlot, chassis, 0),
>>      DEFINE_PROP_UINT16("slot", PCIESlot, slot, 0),
>> -    DEFINE_PROP_UINT16("aer_log_max", PCIESlot,
>> -                       port.br.parent_obj.exp.aer_log.log_max,
>> +    DEFINE_PROP_UINT16("aer_log_max", PCIDevice,
>> +                       exp.aer_log.log_max,
>>                         PCIE_AER_LOG_MAX_DEFAULT),
>>      DEFINE_PROP_END_OF_LIST(),
>>  };
> 
> 
> This looks scary. This does a cast to different types
> without any checks at all.

It doesn't. AFAIU both VMStateDescription and qdev properties store a
numerical offset from the object pointer. CC'ing Juan and Paolo/Anthony.

I.e., if I don't find a counter-example we can drop the arguments from
VMSTATE_PCI_DEVICE() and VMSTATE_PCIE_DEVICE() completely since the
offset would always be 0 and the field name can be hardcoded, cf.
VMSTATE_CPU() in qom/cpu.h.


> What are the advantages of this hack?

The concrete problems I encountered in this series were a) 80 chars
limit and b) parent_obj.parent_obj.foo.
Since offsetof(MyState, parent_obj.foo) == offsetof(ParentState, foo),
this was a neat way to shorten the line.

The main point of the series is introducing abstract QOM types matching
a specific struct. Renaming the parent field helps catch users that
should no longer be accessing it, both in compile-testing and in future
patch review.

What we would do about VMState when someone at some future point wants
to move PCI state into a QOM interface I have no clue, I'll let the
person who throws the first stone worry about that. ;)

Regards,
Andreas

>> @@ -228,7 +225,7 @@ static void ioh3420_class_init(ObjectClass *klass, void *data)
>>  
>>  static const TypeInfo ioh3420_info = {
>>      .name          = "ioh3420",
>> -    .parent        = TYPE_PCI_BRIDGE,
>> +    .parent        = TYPE_PCIE_SLOT,
>>      .instance_size = sizeof(PCIESlot),
>>      .class_init    = ioh3420_class_init,
>>  };
>> diff --git a/hw/pci-bridge/xio3130_downstream.c b/hw/pci-bridge/xio3130_downstream.c
>> index 9acce3f..549ef26 100644
>> --- a/hw/pci-bridge/xio3130_downstream.c
>> +++ b/hw/pci-bridge/xio3130_downstream.c
>> @@ -56,9 +56,8 @@ static void xio3130_downstream_reset(DeviceState *qdev)
>>  
>>  static int xio3130_downstream_initfn(PCIDevice *d)
>>  {
>> -    PCIBridge *br = PCI_BRIDGE(d);
>> -    PCIEPort *p = DO_UPCAST(PCIEPort, br, br);
>> -    PCIESlot *s = DO_UPCAST(PCIESlot, port, p);
>> +    PCIEPort *p = PCIE_PORT(d);
>> +    PCIESlot *s = PCIE_SLOT(d);
>>      int rc;
>>  
>>      rc = pci_bridge_initfn(d, TYPE_PCIE_BUS);
>> @@ -113,9 +112,7 @@ err_bridge:
>>  
>>  static void xio3130_downstream_exitfn(PCIDevice *d)
>>  {
>> -    PCIBridge *br = PCI_BRIDGE(d);
>> -    PCIEPort *p = DO_UPCAST(PCIEPort, br, br);
>> -    PCIESlot *s = DO_UPCAST(PCIESlot, port, p);
>> +    PCIESlot *s = PCIE_SLOT(d);
>>  
>>      pcie_aer_exit(d);
>>      pcie_chassis_del_slot(s);
>> @@ -147,7 +144,7 @@ PCIESlot *xio3130_downstream_init(PCIBus *bus, int devfn, bool multifunction,
>>      qdev_prop_set_uint16(qdev, "slot", slot);
>>      qdev_init_nofail(qdev);
>>  
>> -    return DO_UPCAST(PCIESlot, port, DO_UPCAST(PCIEPort, br, br));
>> +    return PCIE_SLOT(d);
>>  }
>>  
>>  static const VMStateDescription vmstate_xio3130_downstream = {
>> @@ -157,19 +154,19 @@ static const VMStateDescription vmstate_xio3130_downstream = {
>>      .minimum_version_id_old = 1,
>>      .post_load = pcie_cap_slot_post_load,
>>      .fields = (VMStateField[]) {
>> -        VMSTATE_PCIE_DEVICE(port.br.parent_obj, PCIESlot),
>> -        VMSTATE_STRUCT(port.br.parent_obj.exp.aer_log, PCIESlot, 0,
>> +        VMSTATE_PCIE_DEVICE(parent_obj, PCIBridge),
>> +        VMSTATE_STRUCT(exp.aer_log, PCIDevice, 0,
>>                         vmstate_pcie_aer_log, PCIEAERLog),
>>          VMSTATE_END_OF_LIST()
>>      }
>>  };
>>  
>>  static Property xio3130_downstream_properties[] = {
>> -    DEFINE_PROP_UINT8("port", PCIESlot, port.port, 0),
>> +    DEFINE_PROP_UINT8("port", PCIEPort, port, 0),
>>      DEFINE_PROP_UINT8("chassis", PCIESlot, chassis, 0),
>>      DEFINE_PROP_UINT16("slot", PCIESlot, slot, 0),
>> -    DEFINE_PROP_UINT16("aer_log_max", PCIESlot,
>> -                       port.br.parent_obj.exp.aer_log.log_max,
>> +    DEFINE_PROP_UINT16("aer_log_max", PCIDevice,
>> +                       exp.aer_log.log_max,
>>                         PCIE_AER_LOG_MAX_DEFAULT),
>>      DEFINE_PROP_END_OF_LIST(),
>>  };
> 
> 
> Same question.
> 
>> @@ -195,7 +192,7 @@ static void xio3130_downstream_class_init(ObjectClass *klass, void *data)
>>  
>>  static const TypeInfo xio3130_downstream_info = {
>>      .name          = "xio3130-downstream",
>> -    .parent        = TYPE_PCI_BRIDGE,
>> +    .parent        = TYPE_PCIE_SLOT,
>>      .instance_size = sizeof(PCIESlot),
>>      .class_init    = xio3130_downstream_class_init,
>>  };
>> diff --git a/hw/pci-bridge/xio3130_upstream.c b/hw/pci-bridge/xio3130_upstream.c
>> index 6bbcf98..b1ee464 100644
>> --- a/hw/pci-bridge/xio3130_upstream.c
>> +++ b/hw/pci-bridge/xio3130_upstream.c
>> @@ -53,8 +53,7 @@ static void xio3130_upstream_reset(DeviceState *qdev)
>>  
>>  static int xio3130_upstream_initfn(PCIDevice *d)
>>  {
>> -    PCIBridge *br = PCI_BRIDGE(d);
>> -    PCIEPort *p = DO_UPCAST(PCIEPort, br, br);
>> +    PCIEPort *p = PCIE_PORT(d);
>>      int rc;
>>  
>>      rc = pci_bridge_initfn(d, TYPE_PCIE_BUS);
>> @@ -125,7 +124,7 @@ PCIEPort *xio3130_upstream_init(PCIBus *bus, int devfn, bool multifunction,
>>      qdev_prop_set_uint8(qdev, "port", port);
>>      qdev_init_nofail(qdev);
>>  
>> -    return DO_UPCAST(PCIEPort, br, br);
>> +    return PCIE_PORT(d);
>>  }
>>  
>>  static const VMStateDescription vmstate_xio3130_upstream = {
>> @@ -134,8 +133,8 @@ static const VMStateDescription vmstate_xio3130_upstream = {
>>      .minimum_version_id = 1,
>>      .minimum_version_id_old = 1,
>>      .fields = (VMStateField[]) {
>> -        VMSTATE_PCIE_DEVICE(br.parent_obj, PCIEPort),
>> -        VMSTATE_STRUCT(br.parent_obj.exp.aer_log, PCIEPort, 0,
>> +        VMSTATE_PCIE_DEVICE(parent_obj, PCIBridge),
>> +        VMSTATE_STRUCT(exp.aer_log, PCIDevice, 0,
>>                         vmstate_pcie_aer_log, PCIEAERLog),
>>          VMSTATE_END_OF_LIST()
>>      }
>> @@ -143,8 +142,8 @@ static const VMStateDescription vmstate_xio3130_upstream = {
>>  
>>  static Property xio3130_upstream_properties[] = {
>>      DEFINE_PROP_UINT8("port", PCIEPort, port, 0),
>> -    DEFINE_PROP_UINT16("aer_log_max", PCIEPort,
>> -                       br.parent_obj.exp.aer_log.log_max,
>> +    DEFINE_PROP_UINT16("aer_log_max", PCIDevice,
>> +                       exp.aer_log.log_max,
>>      PCIE_AER_LOG_MAX_DEFAULT),
>>      DEFINE_PROP_END_OF_LIST(),
>>  };
> 
> Same question.
> 
> 
>> @@ -170,7 +169,7 @@ static void xio3130_upstream_class_init(ObjectClass *klass, void *data)
>>  
>>  static const TypeInfo xio3130_upstream_info = {
>>      .name          = "x3130-upstream",
>> -    .parent        = TYPE_PCI_BRIDGE,
>> +    .parent        = TYPE_PCIE_PORT,
>>      .instance_size = sizeof(PCIEPort),
>>      .class_init    = xio3130_upstream_class_init,
>>  };
>> diff --git a/hw/pci/pcie_port.c b/hw/pci/pcie_port.c
>> index 91b53a0..a5333a7 100644
>> --- a/hw/pci/pcie_port.c
>> +++ b/hw/pci/pcie_port.c
>> @@ -116,3 +116,25 @@ void pcie_chassis_del_slot(PCIESlot *s)
>>  {
>>      QLIST_REMOVE(s, next);
>>  }
>> +
>> +static const TypeInfo pcie_port_type_info = {
>> +    .name = TYPE_PCIE_PORT,
>> +    .parent = TYPE_PCI_BRIDGE,
>> +    .instance_size = sizeof(PCIEPort),
>> +    .abstract = true,
>> +};
>> +
>> +static const TypeInfo pcie_slot_type_info = {
>> +    .name = TYPE_PCIE_SLOT,
>> +    .parent = TYPE_PCIE_PORT,
>> +    .instance_size = sizeof(PCIESlot),
>> +    .abstract = true,
>> +};
>> +
>> +static void pcie_port_register_types(void)
>> +{
>> +    type_register_static(&pcie_port_type_info);
>> +    type_register_static(&pcie_slot_type_info);
>> +}
>> +
>> +type_init(pcie_port_register_types)
>> diff --git a/include/hw/pci/pcie_port.h b/include/hw/pci/pcie_port.h
>> index d89aa61..e167bf7 100644
>> --- a/include/hw/pci/pcie_port.h
>> +++ b/include/hw/pci/pcie_port.h
>> @@ -24,8 +24,13 @@
>>  #include "hw/pci/pci_bridge.h"
>>  #include "hw/pci/pci_bus.h"
>>  
>> +#define TYPE_PCIE_PORT "pcie-port"
>> +#define PCIE_PORT(obj) OBJECT_CHECK(PCIEPort, (obj), TYPE_PCIE_PORT)
>> +
>>  struct PCIEPort {
>> -    PCIBridge   br;
>> +    /*< private >*/
>> +    PCIBridge   parent_obj;
>> +    /*< public >*/
>>  
>>      /* pci express switch port */
>>      uint8_t     port;
>> @@ -33,8 +38,13 @@ struct PCIEPort {
>>  
>>  void pcie_port_init_reg(PCIDevice *d);
>>  
>> +#define TYPE_PCIE_SLOT "pcie-slot"
>> +#define PCIE_SLOT(obj) OBJECT_CHECK(PCIESlot, (obj), TYPE_PCIE_SLOT)
>> +
>>  struct PCIESlot {
>> -    PCIEPort    port;
>> +    /*< private >*/
>> +    PCIEPort    parent_obj;
>> +    /*< public >*/
>>  
>>      /* pci express switch port with slot */
>>      uint8_t     chassis;
>> -- 
>> 1.8.1.4
> 


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