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Date: Mon, 12 Apr 2010 13:07:39 +0100
From: Jamie Lokier <jamie@shareable.org>
Subject: Re: [Qemu-devel] Problem with QEMU on KVM
Message-ID: <20100412120739.GC18075@shareable.org>
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To: Mulyadi Santosa <mulyadi.santosa@gmail.com>
Cc: Gerhard Wiesinger <lists@wiesinger.com>, qemu-devel@nongnu.org

Mulyadi Santosa wrote:
> Hi Gerhard...
> 
> On Sun, Apr 11, 2010 at 20:52, Gerhard Wiesinger <lists@wiesinger.com> wrote:
> > OK, uses the following ports:
> > Port 0x20: 8259 interrupt controller
> > Port 0x40: 8253 timer
> >
> > Interrupt 0x1A:
> > ah=0x00: fetches system timer counters
> > ah=0x02: reads the clock
> > ah=0x04: fetches date
> >
> > So there must be something wrong with KVM with the above functionality (I
> > guess the timers).
> 
> Hmm, my silly guess is, maybe the timer is seen as decremented....or
> at least "stuck".
> 
> I have very little knowledge about git, but maybe you can start doing
> git bisect to narrow which git commit that introduce such behaviour.
> Meanwhile, let's wait for comments from one of the KVM developers.

There are various -no-kvm-XXX options to try:

-no-kvm-irqchip disable KVM kernel mode PIC/IOAPIC/LAPIC
-no-kvm-pit     disable KVM kernel mode PIT
-no-kvm-pit-reinjection disable KVM kernel mode PIT interrupt reinjection

Any of them might be causing this problem.

They disable in-kernel emulation of the interrupt controller and timer
chips, and force the qemu version to be used.  It's possible the
in-kernel emulation is buggier than the qemu version.

-- Jamie