Re: [Qemu-devel] [PATCH] kvmclock: Ensure time in migration never goes backward

[Marcelo Tosatti <mtosatti@redhat.com>]

Marcin,

Can you provide detailed instructions on how to reproduce the problem? 

Thanks

On Mon, May 05, 2014 at 08:27:10PM -0300, Marcelo Tosatti wrote:
> On Mon, May 05, 2014 at 08:26:04PM +0200, Marcin Gibuła wrote:
> > >>is it possible to have kvmclock jumping forward?
> > >>
> > >>Because I've reproducible case when at about 1 per 20 vm restores, VM freezes for couple of hours and then resumes with date few hundreds years ahead. Happens only with kvmclock.
> > >>
> > >>And this patch seems to fix very similar issue so maybe it's all the same bug.
> > >
> > >I'm fairly sure it is the exact same bug. Jumping backward is like jumping forward by a biiiiig amount :)
> > 
> > Hi,
> > 
> > I've tested your path on my test VM... don't know if it's pure luck
> > or not, but it didn't hang with over 70 restores.
> > 
> > The message "KVM Clock migrated backwards, using later time" fires
> > every time, but VM is healthy after resume.
> 
> What is the host clocksource? (cat
> /sys/devices/system/clocksource/clocksource0/current_clocksource). 
> 
> And kernel version?
>