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Date: Mon, 18 May 2015 21:13:31 -0300
From: Marcelo Tosatti <mtosatti@redhat.com>
To: Sasha Levin <sasha.levin@oracle.com>
Cc: KVM General <kvm@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>, lcapitulino@redhat.com
Subject: Re: kvm: odd time values since "kvmclock: set scheduler clock stable"
Message-ID: <20150519001331.GA15517@amt.cnet>
References: <55528A04.2060404@oracle.com>
 <20150518223936.GA4486@amt.cnet>
 <555A79A5.608@oracle.com>
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GOn Mon, May 18, 2015 at 07:45:41PM -0400, Sasha Levin wrote:
> On 05/18/2015 06:39 PM, Marcelo Tosatti wrote:
> > On Tue, May 12, 2015 at 07:17:24PM -0400, Sasha Levin wrote:
> >> Hi all,
> >>
> >> I'm seeing odd jump in time values during boot of a KVM guest:
> >>
> >> [...]
> >> [    0.000000] tsc: Detected 2260.998 MHz processor
> >> [3376355.247558] Calibrating delay loop (skipped) preset value..
> >> [...]
> >>
> >> I've bisected it to:
> > 
> > Paolo, Sasha,
> > 
> > Although this might seem undesirable, there is no requirement 
> > for sched_clock to initialize at 0:
> > 
> > "
> >  *
> >  * There is no strict promise about the base, although it tends to start
> >  * at 0 on boot (but people really shouldn't rely on that).
> >  *
> > "
> > 
> > Sasha, are you seeing any problem other than the apparent time jump?
> 
> Nope, but I've looked at it again and it seems that it jumps to the host's
> clock (that is, in the example above the 3376355 value was the host's clock
> value).
> 
> 
> Thanks,
> Sasha

Sasha, thats right. Its the host monotonic clock.