Re: Make QEmu HPET disabled by default for KVM?

[Avi Kivity <avi@redhat.com>]

On 03/11/2010 01:56 PM, Avi Kivity wrote:
> On 03/11/2010 12:23 PM, Gleb Natapov wrote:
>>>>
>>>> If the problem it due to lost ticks reinjection may solve it, but 
>>>> only partially.
>>>> What if IO thread haven't run even once during the time vcpu did clock
>>>> source check? IIRC sometimes we trigger this even with in kernel PIT.
>>> That is true.  Reinjection can correct problems in the long term,
>>> but may fail in the short term.  10 ticks is easily short term in a
>>> heavily loaded system.
>>>
>>> How does it happen with kernel PIT?  I could understand it if we had
>>> a work item doing the injection, but everything happens either from
>>> hrtimer context or vcpu context.
>>>
>> Do we kick vcpu out of guest mode when hrtimer triggers? I don't see 
>> us doing it in
>> __kvm_timer_fn().
>>
>
> We're always running on the same cpu as vcpu 0, so no need.
>

Would be better to do it, though, in case we have migration races.

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