Re: [kvm-devel] pv clock: kvm is incompatible with xen :-(

[Gerd H. <kr...@re...>]

Gerd Hoffmann wrote:

> Wall clock is off a few hours though.  Oops.
> 
> I think the way wall clock and system clock work together in xen (Jeremy
> correct me if I'm wrong) is that the wall clock specifies the point in
> time where the system clock started going.  As kvm fills in host system
> time into the guest system time fields the guest wall clock fields
> should be filled with the host boot time timestamp I'd say.

Following up myself with a quick&dirty patch to tackle this issue too.
This one calculates the boot time.  That should be solveable better,
include/linux/time.h lists two functions which sound promising:

  extern void getboottime(struct timespec *ts);
  extern void monotonic_to_bootbased(struct timespec *ts);

Neither of them is available to modules though, so I can't test without
rebooting my laptop ...

monotonic_to_bootbased() sounds like we would get hosts ntp adjustments
in the guests for free.

cheers,
  Gerd

-- 
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