Re: [Linuxptp-devel] Virtual machines

[Richard C. <ric...@gm...>]

On Tue, Oct 01, 2019 at 05:48:41AM +0200, Hans-Heinrich Hansen wrote:
> are there any ideas how LinuxPTP could be used in virtual machines?
> 
> It would be sufficient to be able to use the exact time generated by PTP,
> e.g. with LinuxPTP running on the host system.

On the VM host, simply run ptp4l, ntpd, or chrony etc, as normal.

On the VM guest, enable PTP_1588_CLOCK_KVM (since 4.11), or use
Microsoft Hyper-V guest support (also 4.11+) in a Windows host.

A PHC device representing the host clock will appear in the guest.
Then, for example:

    To configure Chronyd to use PHC refclock, add the
    following line to its configuration file:
    
    refclock PHC /dev/ptpX poll 3 dpoll -2 offset 0
    
    Where /dev/ptpX is the kvmclock PTP clock.

(I have never used this myself, but it is supposed to work!)

HTH,
Richard