On 07/13/2017 04:49 PM, Dr. David Alan Gilbert wrote:
> * Halil Pasic (pa...@linux.vnet.ibm.com) wrote:
>>
>>
>> On 07/13/2017 02:27 PM, Cornelia Huck wrote:
>>>> +static void kvm_flic_ais_pre_save(void *opaque)
>>>> +{
>>>> + KVMS390FLICStateMigTmp *tmp = opaque;
>>>> + KVMS390FLICState *flic = tmp->parent;
>>>> + struct kvm_s390_ais_all ais;
>>>> + struct kvm_device_attr attr = {
>>>> + .group = KVM_DEV_FLIC_AISM_ALL,
>>>> + .addr = (uint64_t)&ais,
>>>> + .attr = sizeof(ais),
>>>> + };
>>>> +
>>>> + if (ioctl(flic->fd, KVM_GET_DEVICE_ATTR, &attr)) {
>>>> + error_report("Failed to retrieve kvm flic ais states");
>>> There's not much else we can do in that case, is there?
>>>
>>
>> I think this is a very good question! The ioctl should not fail
>> under any circumstances, but if it does we have a problem.
>>
>> Carrying on happily (what we do now) means effectively discarding
>> ais state. In general just discarding state ain't a good idea.
>>
>> In particular it might be OK, but the patch should explain that!
>>
>> Regarding what could/should we do in such a case (instead
>> of discarding state and carrying on happily) I don't know, so
>> I tend to agree with you regarding 'not much else we can do'.
>>
>> Adding Dave and Juan. Maybe they can tell.
>
> I keep meaning to make the pre_save give a return value for failure,
> but it hasn't currently got one.
Would you accept patches for that?
>
> You could try something like:
>
> qemu_file_set_error(migrate_get_current()->to_dst_file, -EINVAL);
>
> I *think* the migration code should spot that before it finishes
> but it might carry on for a little while before it does.
I will keep this patch as is, since this is one of the "should not happen"
cases.
