Re: [qemu-s390x] [PATCH v8 4/6] s390x/ap: base Adjunct Processor (AP) object model

[Christian Borntraeger]

On 09/13/2018 08:29 AM, Christian Borntraeger wrote:
>>> +++ b/hw/s390x/ap-bridge.c
>> [...]
>>> +void s390_init_ap(void)
>>> +{
>>> +    DeviceState *dev;
>>> +
>>> +    /* Create bridge device */
>>> +    dev = qdev_create(NULL, TYPE_AP_BRIDGE);
>>> +    object_property_add_child(qdev_get_machine(), TYPE_AP_BRIDGE,
>>> +                              OBJECT(dev), NULL);
>>> +    qdev_init_nofail(dev);
>>> +
>>> +    /* Create bus on bridge device */
>>> +    qbus_create(TYPE_VFIO_AP_BUS, dev, TYPE_VFIO_AP_BUS);
>>> + }
>> [...]
>>> +type_init(ap_device_register)
>>> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
>>> index f0f7fdc..3c100c2 100644
>>> --- a/hw/s390x/s390-virtio-ccw.c
>>> +++ b/hw/s390x/s390-virtio-ccw.c
>>> @@ -32,6 +32,7 @@
>>>  #include "ipl.h"
>>>  #include "hw/s390x/s390-virtio-ccw.h"
>>>  #include "hw/s390x/css-bridge.h"
>>> +#include "hw/s390x/ap-bridge.h"
>>>  #include "migration/register.h"
>>>  #include "cpu_models.h"
>>>  #include "hw/nmi.h"
>>> @@ -263,6 +264,9 @@ static void ccw_init(MachineState *machine)
>>>      /* init the SIGP facility */
>>>      s390_init_sigp();
>>>  
>>> +    /* create AP bridge and bus(es) */
>>> +    s390_init_ap();
>>> +
>>
>> Not sure since there is no explicit migration state involved here, but I
>> think you cannot simply create the ap-bridge device always
>> unconditionally, can you? Did you check whether you can ping-pong
>> migrate an guest that runs on an older version of QEMU to a QEMU that
>> contains this patch and back? If it does not work, it might be necessary
>> to restrict this ap-bridge device for new machine types only, I think.
> 
> We have already the cpu features at this point in time. So simply doing

s/doing/checking/

> s390_has_feat(S390_FEAT_AP) in s390_init_ap ?
>