linux-kernel - Re: kvm: odd time values since "kvmclock: set scheduler clock stable"

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20150519001331.GA15517@amt.cnet>
Date:	Mon, 18 May 2015 21:13:31 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	KVM General <kvm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Paolo Bonzini <pbonzini@...hat.com>, lcapitulino@...hat.com
Subject: Re: kvm: odd time values since "kvmclock: set scheduler clock stable"

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.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/