Thomas Gleixner wrote:

Ooops. I completely forgot, that you get the absolute expiry time
already in ktime_t format (nanoseconds) when dev->set_next_event() is
called.

	dev->next_event = expires;

is done right before the call. 

So it's already there for free.
  

OK, but a trap for young players (ie, me): the absolute time is in ns
since kernel boot, but the hypervisor wants an absolute time in ns since
system boot.  Everything works reasonably well for the first guest
started early, so be sure to take a snapshot of hypervisor time early in
order to get the correction...

    J