[Qemu-devel] [PATCH 0/2 v5] 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': 'int' }

{ 'command': 'guest-set-time', 'data': { 'time': int } }

Notes:
For the implementition of win32-specific commands, I plan
to send it out in another thread later.

Suggestions and comments are welcome!

Changes since v4:
  - Fix the missing error exit pointed by Eric.
  - Doc improvement from Eric.

Changes since v3:
  - Doc improvement based on Eric's suggestions.
  - Overflow check improve from Eric. 

Changes since v2:
  - Get rid of utc-offset, and make it just pass single nanoseconds
    relative to the Epoch in UTC/GMT according to Anthony and
    Eric's comments.
  - Make time argument mandatory.
  - Fix the overflow check for year-2038 problem.
  - Error handel improvment from Eric. 

Changes since v1:
  - Squashed patches add support to get host time and add
    guest-get-time command into one.
  - Documents improvment based on the suggestions from
    Eric and Mike.
  - Change the name of 'HostTimeInfo' to 'TimeInfo'.
  - Better use-case and logic for 'guest-set-time'
    command suggested by Eric.
  - Error handel improvment from Luiz.

Lei Li (2):
  qga: add guest-get-time command
  qga: add guest-set-time command