Re: regression - 2.6.36 -> 2.6.37 - kvm - 32bit SMP guests don'tboot

[Zachary Amsden]

On 03/04/2011 02:09 PM, Glauber Costa wrote:
> On Fri, 2011-03-04 at 19:27 +0100, Nikola Ciprich wrote:
>    
> > Hello Zachary,
> >
> >      
> > > You don't see any messages about TSC being unstable or switching
> > > clocksource after loading the KVM module?  And you are not suspending
> > > the host or anything?
> > >        
> > no messages, no suspending, nothing.
> >
> >
> >      
> > > Can you try using "processor.max_cstate=1" on the host as a kernel
> > > parameter and see if it makes a difference?
> > >        
> > I tried it, no change..
> > n.
> >      
> Zach,
>
> I don't understand 100 % the logic behind all your tsc changes.
> But kvm-clock-wise, most of the problems we had in the past were related
> to the difference in resolution between the tsc and the host clocksource
> (hpet, acpi_pm, etc), which in his case, it is a non-issue.
>
> It does seem to me like some compensation logic kicked in, dismantling
> an otherwise good tsc. He does have nonstop_tsc, which means it can't
> get any better.
>
> One thing I noticed when reading the culprit patch in bisect, is that in
> vcpu_load(), there were previously a call to
>
>   kvm_request_guest_time_update(vcpu)
>
> that was removed without a counterpart addition. Any idea about why it
> was done?
>    

That's probably the source of the bug... I've been looking for that 
exact line, though, and I can't find it missing.
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