Re: [Xen-devel] [PATCH 1/3] xen/arm: introduce xen_read_wallclock

[Arnd Bergmann <arnd@xxxxxxxx>]

On Monday 09 November 2015 13:53:30 Stefano Stabellini wrote:
> On Fri, 6 Nov 2015, Arnd Bergmann wrote:
> > I'm not quite sure about how the split between pvclock_wall_clock and
> > the delta works. Normally I'd expect that pvclock_wall_clock is the 
> > wallclock
> > time as it was at boot, while delta is the number of expired nanoseconds
> > since boot. However it is unclear why the latter has a longer range
> > (539 years starting at boot, rather than 126 years starting in 1970).
> 
> Actually we already have a sec overflow field in struct shared_info on
> the hypervisor side, called wc_sec_hi. I just need to make use of it in
> Linux. See:
> 
> http://xenbits.xen.org/gitweb/?p=xen.git;a=blob_plain;f=xen/include/public/xen.h;hb=HEAD
> 
> Thanks for raising my attention to the problem,

Sounds good for Xen on ARM. This same interface is also used on
KVM, right? Does the extension also work there?

        Arnd

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