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Date: Thu, 27 Aug 2009 11:24:37 +0300
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 2/2] Route IOAPIC interrupts via ISA bus
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To: Jamie Lokier <jamie@shareable.org>
Cc: qemu-devel@nongnu.org, Gerd Hoffmann <kraxel@redhat.com>, Avi Kivity <avi@redhat.com>

On Thu, Aug 27, 2009 at 09:18:32AM +0100, Jamie Lokier wrote:
> Gleb Natapov wrote:
> > On Thu, Aug 27, 2009 at 09:40:06AM +0200, Gerd Hoffmann wrote:
> > >            Or does it mean we must emulate a more recent chipset?
> > > 
> > That too will work.
> 
> 
> Note that if you change the chipset, it'll break some existing Windows VMs.
> 
I don't think it worth changing chipset just to solve irq routing
problem. And PIIX4 is the same as PIIX3 in regards to pci irq routing. 

> I had this problem when porting a Windows Server 2003 VM from Virtual
> PC to QEMU: Virtual PC emulates a PIIX4, while QEMU provides a PIIX3
> (even though there's a PIIX4 in the source code, it's not used for PC
> emulation).  The ported image would not boot because of the change of
> chipset, until I patched the registry to accomodate the change.
> 
> It will be the same the other way: When some Windows VMs see a change
> from PIIX3 to a later chipset, they will not boot.
> 
> Some Windows VMs don't care as much.  XP seems to be more like Linux,
> in that it adapts to different devices at boot time.
> 
> -- Jamie
> 
> 
> 
> 
> > 
> > --
> > 			Gleb.
> > 
> > 

--
			Gleb.