[Qemu-devel] [RFC PATCH 0/3] Time resync support by qemu-ga

[Lei Li]

This patch series attempts to add time resync support
to qemu-ga by introducing qemu-ga commands guest-get-time
and guest-set-time.

Right now, when a guest is paused or migrated to a file
then loaded from that file, the guest OS has no idea that
there was a big gap in the time. Depending on how long the
gap was, NTP might not be able to resynchronize the guest.
So adding new guest-agent command that is called any time
a guest is resumed  and which tells the guest to update its
own wall clock time based on the information from the host
will make it easier for a guest to resynchronize without
waiting for NTP.

The previous RFC send for discussion and suggestion as link
here:

http://article.gmane.org/gmane.comp.emulators.qemu/186126

The interface for these commands like:

{ 'command': 'guest-get-time', 'returns': 'HostTimeInfo' }

{ 'command': 'guest-set-time',
  'data': { '*seconds': 'int', '*microseconds': 'int',
            '*utc-offset': 'int' } }

TODO:
This is a RFC version with POSIX-specific command implemented.
I just test on Linux guest, will add win32-specific command to
support Windows guest later. Since I want to make sure if this
seems like the way we should be headed.

Your comments and suggestions are very welcome!

Lei Li (3):
  qga: add support to get host time
  qga: add guest-get-time command
  qga: add guest-set-time command