Messages in this thread | | | From | Vivek Thampi <> | Subject | Re: [PATCH RESEND] ptp: add VMware virtual PTP clock driver | Date | Thu, 5 Mar 2020 04:47:28 +0000 |
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Thanks for taking a look, David.
On Wed, Mar 04, 2020 at 02:04:10PM -0800, David Miller wrote: > From: Vivek Thampi <vithampi@vmware.com> > Date: Fri, 28 Feb 2020 05:32:46 +0000 > > > Add a PTP clock driver called ptp_vmw, for guests running on VMware ESXi > > hypervisor. The driver attaches to a VMware virtual device called > > "precision clock" that provides a mechanism for querying host system time. > > Similar to existing virtual PTP clock drivers (e.g. ptp_kvm), ptp_vmw > > utilizes the kernel's PTP hardware clock API to implement a clock device > > that can be used as a reference in Chrony for synchronizing guest time with > > host. > > > > The driver is only applicable to x86 guests running in VMware virtual > > machines with precision clock virtual device present. It uses a VMware > > specific hypercall mechanism to read time from the device. > > > > Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com> > > Signed-off-by: Vivek Thampi <vithampi@vmware.com> > > --- > > Based on feedback, resending patch to include a broader audience. > > If it's just providing a read of an accurate timesource, I think it's kinda > pointless to provide a full PTP driver for it.
The point of a PTP driver for this timesource is to provide an interface that can be consumed by Chrony (and possibly other applications) as a reference clock for time sync. This is admittedly a very basic first step providing just PTP_SYS_OFFSET functionality (which gets us to <1us VM-host time sync). Down the line, I also intend to introduce cross-timestamping for more precise offsets.
Using the PHC infrastructure seems like a good fit for this, but please let me know if I'm missing something or misinterpreting your comment.
Thanks.
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