Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with Win7: hpet missing time drift fixups

[Gleb Natapov]

On Mon, Jul 05, 2010 at 04:42:06PM +0300, Avi Kivity wrote:
> On 07/05/2010 04:24 PM, Jan Kiszka wrote:
> >
> >But how to deal with multiple acks per input due to multiple open
> >outputs (not just to different CPUs)?
> 
> That will be very rare (i.e. guest bug).
> 
> >We either need to enable the
> >router to filter redundant information or support the injection source
> >with processing all acks properly.
> >
> >And is there some scenario where the time-keeping device is sharing its
> >IRQ line with some other device? De-coalescing workarounds would not
> >work then if they were notifier based.
> 
> In that case the timekeeping device needs to expose some kind of
> register the guest reads, to distinguish among the various sources.
> If that's the case, then the qemu timekeeping code can look at
> accesses to this register instead of acks/deliveries.
> 
RTC has such register, but Windows access it more the once on each
interrupt and that makes counting on this access unreliable for interrupt
decoalescing.

--
                        Gleb.