Re: [PATCH] KVM: halt-polling: poll if emulated lapic timer will fire soon

[Wanpeng Li]

2016-05-19 19:42 GMT+08:00 Christian Borntraeger <borntraeger@xxxxxxxxxx>:
> On 05/19/2016 01:35 PM, Wanpeng Li wrote:
>> 2016-05-19 19:23 GMT+08:00 Christian Borntraeger <borntraeger@xxxxxxxxxx>:
>>> On 05/19/2016 11:26 AM, Wanpeng Li wrote:
>>>
>>> I think in general a good idea to poll if a timer will expire soon.
>>>
>>> Some patch comments:
>>>
>>> Same for all non-x86 archs:
>>>> +static inline unsigned int kvm_arch_timer_remaining(struct kvm_vcpu *vcpu) {}
>>>
>>> A function returning int, without a return statement?
>>> That gives at least a compiler warning.
>>
>> How about return 0 for all non-x86 archs?
>
> We will provide an s390 implementation soon, but until then a proper
> default would be good.
>
> [....]
>>>> +     if (vcpu->halt_poll_ns || (remaining < halt_poll_ns_base)) {
>
> but then remaining is 0 and the 2nd condition will always be true, no?

Nice catch!

How about something like below:

+       if (vcpu->halt_poll_ns ||
+               (remaining != 0 && remaining < halt_poll_ns_base)) {

Regards,
Wanpeng Li