Messages in this thread | | | Date | Tue, 23 Dec 2014 11:25:08 +0100 | From | Paolo Bonzini <> | Subject | Re: Cleaning up the KVM clock |
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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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