Re: [Qemu-devel] [PATCH v2 1/2] s390x/ais: enable ais when migration is available

[Christian Borntraeger]

On 09/26/2017 03:43 PM, David Hildenbrand wrote:
> 
>> +    /* try enable the AIS facility */
>> +    test_attr.group = KVM_DEV_FLIC_AISM_ALL;
>> +    if (!ioctl(flic_state->fd, KVM_HAS_DEVICE_ATTR, test_attr)) {
>> +            kvm_vm_enable_cap(kvm_state, KVM_CAP_S390_AIS, 0);
>> +    }
>> +
>>      return;
>>  fail:
>>      error_propagate(errp, errp_local);
>> @@ -578,7 +584,7 @@ static void kvm_s390_flic_reset(DeviceState *dev)
>>  
>>      flic_disable_wait_pfault(flic);
>>  
>> -    if (fs->ais_supported) {
>> +    if (s390_has_feat(S390_FEAT_ADAPTER_INT_SUPPRESSION)) {
> 
> I don't remember if a reset is trigger on realization. Most probably
> not, but it could be.
> 
> Would it hurt if the following code would not get called if the flic
> hasn't been used yet? (possible reset before cpu model has been
> initialized) - are kvm_s390_modify_ais_mode() calls required before ais
> can be used for the first time?

Hmm, simm/nimm should default to zero in the kernel I guess. So I think it would
not hurt. Yi Min, correct?


Anyway it seems that reset is NOT called during realize, the first
call is

                #0  0x00000000010e5178 kvm_s390_flic_reset (qemu-system-s390x)
                #1  0x000000000124bbc4 device_reset (qemu-system-s390x)
                #2  0x0000000001248cd0 qdev_reset_one (qemu-system-s390x)
                #3  0x0000000001249ea4 qdev_walk_children (qemu-system-s390x)
                #4  0x000000000124fd3a qbus_walk_children (qemu-system-s390x)
                #5  0x0000000001248e6c qbus_reset_all (qemu-system-s390x)
                #6  0x0000000001248eae qbus_reset_all_fn (qemu-system-s390x)
                #7  0x0000000001250a60 qemu_devices_reset (qemu-system-s390x)
                #8  0x0000000001143c80 s390_machine_reset (qemu-system-s390x)
                #9  0x00000000011c5b72 qemu_system_reset (qemu-system-s390x)
                #10 0x00000000011ceb8e main (qemu-system-s390x)
                #11 0x000003ff947a289a __libc_start_main (libc.so.6)
                #12 0x0000000001017646 _start (qemu-system-s390x)