Re: [Qemu-devel] [PATCH v2 0/3] Let RTC follow backward jumps of host clock immediately

[Anthony Liguori <aliguori@us.ibm.com>]

On 06/20/2011 07:06 AM, Jan Kiszka wrote:
> Just noticed that this issue is still unfixed because my series was
> somehow forgotten. So I've rebased it over current master, refactored it
> to use the generic Notifier infrastructure and renamed it to "clock
> reset notifier" to avoid confusion with icount related "warping". Please
> review / apply before 0.15-rc0, it fixes a relevant issue.
>
> Original series description:
>
> By default, we base the mc146818 RTC on the host clock (CLOCK_REALTIME).
> This works fine if only the frequency of the host clock is tuned (e.g.
> by NTP) or if it is set to a future time. However, if the host is tuned
> backward, e.g. because NTP obtained the correct time after the guest was
> already started or the admin decided to tune the local time, we see an
> unpleasant effect in the guest: The RTC will stall for the period the
> host clock is set back. We identified that one prominent guest affected
> by this is Windows which relies on the periodic RTC interrupt for time
> keeping.
>
> This series address the issue by detecting those warps and providing a
> callback mechanism to device models. The RTC is enabled to update its
> timers and register content immediately. Tested successfully both with
> hwclock in a Linux guest and by monitoring the Windows clock while
> fiddling with the host time.
>
> Note that if this kind of RTC adjustment is not wanted, the user is
> still free to decouple the RTC from the host clock and base it on the
> VM clock - just like before.
>
> Jan Kiszka (3):
>    notifier: Pass data argument to callback
>    qemu-timer: Introduce clock reset notifier
>    mc146818rtc: Handle host clock resets

Applied.  Thanks.

Regards,

Anthony Liguori

>
>   hw/fw_cfg.c      |    2 +-
>   hw/mc146818rtc.c |   20 ++++++++++++++++++++
>   input.c          |    2 +-
>   migration.c      |   12 ++++++------
>   notify.c         |    4 ++--
>   notify.h         |    4 ++--
>   qemu-timer.c     |   29 ++++++++++++++++++++++++++++-
>   qemu-timer.h     |    5 +++++
>   ui/sdl.c         |    2 +-
>   ui/spice-core.c  |    2 +-
>   ui/spice-input.c |    4 ++--
>   ui/vnc.c         |    4 ++--
>   usb-linux.c      |    2 +-
>   vl.c             |    4 ++--
>   xen-all.c        |    2 +-
>   15 files changed, 75 insertions(+), 23 deletions(-)
>
>
>