Re: [PATCH 1/5] Add a global synchronization point for pvclock

Avi Kivity
2010-04-19T10:54:15Z

On 04/19/2010 01:51 PM, Peter Zijlstra wrote:
>
>
>>> Right, so on x86 we have:
>>>
>>> X86_FEATURE_CONSTANT_TSC, which only states that TSC is frequency
>>> independent, not that it doesn't stop in C states and similar fun stuff.
>>>
>>> X86_FEATURE_TSC_RELIABLE, which IIRC should indicate the TSC is constant
>>> and synced between cores.
>>>
>>>
>>>
>> Sockets and boards too? (IOW, how reliable is TSC_RELIABLE)?
>>
> Not sure, IIRC we clear that when the TSC sync test fails, eg when we
> mark the tsc clocksource unusable.
>

Worrying. By the time we detect this the guest may already have gotten
confused by clocks going backwards.

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error compiling committee.c: too many arguments to function