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    SubjectRe: [PATCH 1/5] Add a global synchronization point for pvclock
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    On Mon, 2010-04-19 at 12:46 +0200, Peter Zijlstra wrote:
    > On Sat, 2010-04-17 at 21:48 +0300, Avi Kivity wrote:
    > > > After this patch is applied, I don't see a single warp in time during 5 days
    > > > of execution, in any of the machines I saw them before.
    > > >
    > > >
    > >
    > > Please define a cpuid bit that makes this optional. When we eventually
    > > enable it in the future, it will allow a wider range of guests to enjoy it.
    >
    > 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.

    Fun, we also have:

    X86_FEATURE_NONSTOP_TSC, which states the thing doesn't stop in C
    states.



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