On Wed, Sep 19, 2012 at 06:34:46PM +0300, Avi Kivity wrote: > On 09/16/2012 05:37 PM, Anthony Liguori wrote: > > Avi Kivity <a...@redhat.com> writes: > > > >> On 09/13/2012 09:27 PM, Anthony Liguori wrote: > >>> If there was a better/equivalent solution that didn't depend on qemu-ga, > >>> I'd be all for it. But there isn't AFAICT. > >> > >> Perhaps there is. We fixed the problem for Linux by adding kvmclock and > >> backporting it to distros that users are most likely to use. Windows > >> fixed the problem by adding their own pv clock interface. So we need to > >> implement that, then focus on tick catchup for Windows XP and other > >> guests with no pv interface (*BSD, etc.) > > > > Tick catchup simply isn't going to work. That's the whole point of the > > thread. > > I'll restate. Windows and Linux don't need either qemu-ga or tick > catchup since they have pv time interfaces. FreeBSD and less frequently > used guests are unlikely to get a qemu-ga port, so they need tick > catchup. Is there reason to believe tick catchup won't work on FreeBSD? > If FreeBSD tries to compensate for lost ticks it may not work.
> >> > >> Those older guests are also less likely to have a qemu-ga port or > >> administrator motivation to install it. > > > > That's a strange assertion to make. FWIW, the issue with hibernation > > was reported to me with a combination of WinXP and Windows 7 guests, in > > this case, it's a totally new deployment. Adding qemu-ga is totally > > reasonable. > > Windows 7 doesn't need anything if we implement the pv time interface. What PV interface exactly? According to [1] Hyper-v also tries to "catch-up" timer by shortening timer period unless to many events were missed. [1] http://msdn.microsoft.com/en-us/library/windows/hardware/ff542561%28v=vs.85%29.aspx > That is less effort than requiring a qemu-ga installation. Windows XP > is an edge case. We can of course support qemu-ga for it, or we can > massage the tick code to work with it, since it's timekeeping is likely > a lot less sophisticated than 7's. > How do you propose to "massage the tick code" to compensate for 100 hours of missed ticks in a sane way? As far as I know there is no difference in timekeeping between Windows XP and Windows 7 (at least without PV). -- Gleb.
