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Date: Mon, 5 Aug 2013 13:10:04 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/2] memory: Provide separate handling of
 unassigned io ports accesses
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Jan Kiszka <jan.kiszka@web.de>, Andreas =?utf-8?Q?F=C3=A4rber?= <afaerber@suse.de>, Aurelien Jarno <aurelien@aurel32.net>, qemu-devel <qemu-devel@nongnu.org>

On Aug 05 2013, Peter Maydell wrote:
> > But even if we would, the IO container now catches all accesses, so
> > the system memory region will never have its default handler run for
> > that window.
> 
> Yes, that is the point -- before the IO container caught all
> accesses, the default handler that would run would be the
> system memory region, but now that the IO container has
> default read/write ops they will take precedence. So this
> would be a behaviour change if there are any boards set up
> like this. (I'm not sure there are any, though.)

Before 1.6 this would have happened anyway.  Before 1.6, all
I/O accesses would go through cpu_in/cpu_out, and would never
hit the system memory region.  So Jan's patch is effectively
restoring old behavior.

Paolo