On Wed, Feb 24, 2016 at 03:27:45PM +0000, Avi Cohen wrote: > > > >Subtracting tsc_offset later is easier. > > >> In guest : rx_time = tsc_to_ns * rdtsc() > >> Delay = rx_time - tx_time > >> > >> How to enable kvm_write_tsc_offset ? > > ># echo kvm_write_tsc_offset > /sys/kernel/debug/tracing/set_event > > >Then boot guest > > >Then cat /sys/kernel/debug/tracing/trace > > OK - I did it and it is indeed accurate. But this will not solve my problem, because I need the host realtime clock in my guest and not the host-TSC Configure NTP to synchronize from host NTPd server. How close the host and guest clocks can be synchronized depends on how reliable is the transmission of data between guest and host. Then use the guest/host TSCs to measure how accurate the clocks are. > In my application VMa in HOSTa is sending a 1-way delay measurement packet to VMb in HOSTb. > I'm perfectly synching the 2 hosts with PTP. > I need that the 2 guests's clocks will be synched to their hosts i.e. VMa/VMb is sync to HOSTa/HOSTb accordingly Chronyd in the guest should work, syncing from NTPd server in the host (haven't configured that setup myself, about to do so soon). -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
