Re: [PATCH v1 7/7] kvm/x86: Hyper-V SynIC timers

[Andrey Smetanin <asmetanin@virtuozzo.com>]

On 11/27/2015 01:49 PM, Paolo Bonzini wrote:
>
>
> On 27/11/2015 09:12, Roman Kagan wrote:
>>>> +	n = div64_u64(time_now - stimer->exp_time, stimer->count) + 1;
>>>> +	stimer->exp_time += n * stimer->count;
>> This is actually just a reminder calculation so I'd rather do it
>> directly with div64_u64_rem().
>
> It took me a while to understand why it was a remained. :)  Expanding
> Andrey's formula you get
>
> 	exp_time = exp_time + count + (time_now - exp_time) / count * count
>
> the remainder, (time_now - exp_time) % count would be
>
> 	time_now - exp_time - (time_now - exp_time) / count * count
>
> so -((time_now - exp_time) % count) is
>
> 	exp_time - time_now + (time_now - exp_time) / count * count
>
> so Andrey's expression is
>
> 	exp_time = time_now + (count - (time_now - exp_time) % count)
>
> Yeah, that looks nice.
I'll redo this way.
>
> Paolo
>