Re: [Xen-devel] syncing wall clock time from Dom0 to hypervisor

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2011-07-13 at 14:52 +0100, Konrad Rzeszutek Wilk wrote:
> On Thu, Jun 30, 2011 at 11:16:17AM +0100, Jan Beulich wrote:
> > While in the upstream kernel I'm unable to find any use of XENPF_settime
> > (and the DOM0_SETTIME alias of it) at all, in the 2.6.18 tree (and the
> > forward ports of it) the function gets used only when ntp_synced()
> > returns true (and - that's minor - when independent_wallclock is not
> > set).
> > 
> > It would however seem to me that this doesn't cover the case where
> > the host clock gets adjusted by the Dom0 admin. Is there perhaps
> > someone who remembers whether this was implemented the way it
> > is intentionally?
> 
> <groan> I think we just forgot.

Was this what Stefano's patch from way back was about:
http://lists.xensource.com/archives/html/xen-devel/2010-02/msg00469.html
?

I forget what the issue with it was and the conversation got derailed
about into talking about an adjtimex style hypercall

Ian.

> 
> Looking at xen_set_wallclock it just looks as we need to make it do
> a similar hypercall as the sync_xen_wallclock to update it?
> 
> > 
> > There's no such restriction in Jeremy's tree, but that tree also doesn't
> > seem to be doing updates at regular intervals (for NTP), nor does it
> > look like the CMOS clock would get updated here at all (i.e. I can't
> > really take this as a proper reference either).
> 
> I think the 'sync_cmos_clock' looks to be doing that. And the hook
> to the Xen is via 'update_persistent_clock' call?
> 
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