> -----Original Message----- > From: Richard Cochran [mailto:richardcochran@xxxxxxxxx] > Sent: Tuesday, October 21, 2014 4:14 PM > To: Thomas Shao > Cc: Thomas Gleixner; gregkh@xxxxxxxxxxxxxxxxxxx; LKML; > devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx; apw@xxxxxxxxxxxxx; > jasowang@xxxxxxxxxx; KY Srinivasan; John Stultz; Richard Cochran > Subject: Re: [PATCH v2 1/2] timekeeping: add EXPORT_SYMBOL_GPL for > do_adjtimex() > > On Tue, Oct 21, 2014 at 03:18:58AM +0000, Thomas Shao wrote: > > > > In some situation, the user is not able to enable guest VM to sync > > with external time source, like NTP. But the host is still synced with a > trusted time source. > > But the guest *is* networked, right? > > (Otherwise syncing the guest's clock is pointless.) > I believe it should be a valid scenario, that NTP is not available in the client, and we want the guest time sync with host. Other hypervisor like Xen, VMWare also provide the host-guest time sync feature. > > I've got some feedbacks from Richard and Mike, including reference NTP > > implementation and do the adjustment in the host side. I've already > > referenced some NTP design in my patch. I would consider my patch as a > simplified implementation. > > I really don't think we want a half baked servo in some random driver. > Instead, why not present the time difference using a standard interface? OK. I'll do more investigation. Could you let me know what's the standard interface for presenting time difference you mentioned here? Thanks! > > > I've also considered > > the host side implementation. But in host, we can only set time but > > not gradually slew/adjust time, > > Why not implement adjustment in the host? > > > which is not acceptable for the time sync solution.We still recommend > > user to configure NTP on the guest, which provides better accuracy. > > But if NTP is not applicable, this could be another option. > > You did not really answer any of my objections, nor did you consider the > alternative ideas which I offered. Would you care to address those? I do not agree the guest VM time adjustment should be handled by the host. In my opinion, the host should not involve in any Guest OS level operation. > > Thanks, > Richard _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
