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Date: Mon, 5 Jul 2010 16:44:29 +0300
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [Qemu-devel] Re: [Bug 599958] Re: Timedrift problems with
	Win7: hpet missing time drift fixups
Message-ID: <20100705134429.GS4689@redhat.com>
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To: Avi Kivity <avi@redhat.com>
Cc: Blue Swirl <blauwirbel@gmail.com>, Jan Kiszka <jan.kiszka@siemens.com>, Paul Brook <paul@codesourcery.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

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.