Re: kvmclock doesn't work, help?

Andy Lutomirski
2015-12-16T17:48:27Z

On Tue, Dec 15, 2015 at 12:42 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
>
> On 14/12/2015 23:31, Andy Lutomirski wrote:
>> > RAW TSC NTP corrected TSC
>> > t0 10 10
>> > t1 20 19.99
>> > t2 30 29.98
>> > t3 40 39.97
>> > t4 50 49.96
>> >
>> > ...
>> >
>> > if you suddenly switch from RAW TSC to NTP corrected TSC,
>> > you can see what will happen.
>>
>> Sure, but why would you ever switch from one to the other?
>
> The guest uses the raw TSC and systemtime = 0 until suspend. After
> resume, the TSC certainly increases at the same rate as before, but the
> raw TSC restarted counting from 0 and systemtime has increased slower
> than the guest kvmclock.

Wait, are we talking about the host's NTP or the guest's NTP?

If it's the host's, then wouldn't systemtime be reset after resume to
the NTP corrected value? If so, the guest wouldn't see time go
backwards.

If it's the guest's, then the guest's NTP correction is applied on top
of kvmclock, and this shouldn't matter.

I still feel like I'm missing something very basic here.

--Andy