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

From: Nikola Ciprich
Date: Fri Mar 04 2011 - 15:55:32 EST


> 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?
>
> Nikola, does adding that line back alleviate the problem for you ?
Hello Glauber,
kvm_request_guest_time_update seems to have been renamed and then
removed since then, but I've added
kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
instead and now the guest boots!
So maybe missing clock update is really the culprit here?
What do You guys think?
n.



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