Re: [Qemu-devel] [PATCH/RFC 2/3] s390x/ais: enable ais when migration is available

[David Hildenbrand <david@redhat.com>]

On 26.09.2017 14:29, Christian Borntraeger wrote:
> 
> 
> On 09/26/2017 02:23 PM, David Hildenbrand wrote:
>> On 22.09.2017 10:38, Christian Borntraeger wrote:
>>> Instead of unconditionally enabling the KVM AIS capability
>>> in the kvm arch init function, do this in the flic realize function
>>> when we know if migration is available. This requires to initialize
>>> flic before the CPUs.
>>>
>>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>>> ---
>>>  hw/intc/s390_flic.c          | 11 +++++++++--
>>>  hw/intc/s390_flic_kvm.c      |  8 +++++++-
>>>  hw/s390x/s390-virtio-ccw.c   |  8 ++++++--
>>>  include/hw/s390x/s390_flic.h |  1 +
>>>  target/s390x/cpu_models.c    |  6 ++++++
>>>  target/s390x/kvm.c           |  8 +-------
>>>  6 files changed, 30 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/hw/intc/s390_flic.c b/hw/intc/s390_flic.c
>>> index 6eaf178..08040fe 100644
>>> --- a/hw/intc/s390_flic.c
>>> +++ b/hw/intc/s390_flic.c
>>> @@ -1,7 +1,7 @@
>>>  /*
>>>   * QEMU S390x floating interrupt controller (flic)
>>>   *
>>> - * Copyright 2014 IBM Corp.
>>> + * Copyright 2014,2017 IBM Corp.
>>>   * Author(s): Jens Freimann <jfrei@linux.vnet.ibm.com>
>>>   *            Cornelia Huck <cornelia.huck@de.ibm.com>
>>>   *
>>> @@ -49,6 +49,13 @@ void s390_flic_init(void)
>>>      qdev_init_nofail(dev);
>>>  }
>>>  
>>> +void s390_flic_enable_ais(void)
>>> +{
>>> +    S390FLICState *fs = s390_get_flic();
>>> +
>>> +    fs->ais_supported = true;
>>
>> Can we simply replace all ais_supported checks by
>> s390_has_feat(S390_FEAT_ADAPTER_INT_SUPPRESSION) and drop ais_supported?
> 
> No, at flic realize, the CPU model is not available yet. And if we move cpumodel
> before flic then we cannot check the flic attributes so the CPU will not know if
> ais is available or not.
> 

We should we need that at realize time?

realize() simply inits flic and unlocks the CPU feature if
KVM_HAS_DEVICE_ATTR works.

What am I missing?

-- 

Thanks,

David