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SubjectRe: Cleaning up the KVM clock


On 23/12/2014 11:23, Santosh Shukla wrote:
>
>
> No. kvm_guest_time_update is called by vcpu_enter_guest, while the vCPU
> is not running, so it's entirely atomic from the point of view of
> the guest.
>
>
> Then checking odd value for version field (at guest side: function
> pvclock_clocksource_read / pvclock_read_flag) is redundant considering
> that kvm_guest_time_update incremented by 2.

The code is common to Xen and KVM. Xen uses seqlock semantics. The
cost of one AND is not detectable.

Paolo


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