linux-kernel - Re: [PATCH 2/2] add sysctl for kvm wallclock sync

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Message-ID: <20090902113124.GK30340@mothafucka.localdomain>
Date:	Wed, 2 Sep 2009 08:31:24 -0300
From:	Glauber Costa <glommer@...hat.com>
To:	Chris Lalancette <clalance@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, avi@...hat.com
Subject: Re: [PATCH 2/2] add sysctl for kvm wallclock sync

On Wed, Sep 02, 2009 at 08:54:37AM +0200, Chris Lalancette wrote:
> Glauber Costa wrote:
> > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
> > index fc409e9..3a4e1bd 100644
> > --- a/arch/x86/kernel/kvmclock.c
> > +++ b/arch/x86/kernel/kvmclock.c
> > @@ -27,7 +27,7 @@
> >  #define KVM_SCALE 22
> >  
> >  static int kvmclock = 1;
> > -static unsigned int kvm_wall_update_interval = 5;
> > +unsigned int kvm_wall_update_interval = 5;
> 
> I think the overall idea is very interesting, but I also think that it should be
> disabled by default.  Because of the problems with time in virtualization,
> people are already conditioned to run ntpd inside their guests, and this
> kvmclock change will "fight" with ntpd.  Also, the command "# date 09091323" (or
> whatever) ceases to work like it does on bare-metal, so I think it has to be an
> opt-in feature.
I don't disagree.

Actually, I thought about that myself a few hours after I sent the patch. 
Avi, do you have a word on that ?
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