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From: Marcel Apfelbaum <marcel.a@redhat.com>
Date: Mon, 09 Sep 2013 16:15:37 +0300
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Subject: Re: [Qemu-devel] [PATCH RFC v2 2/2] hw/pci: handle unassigned pci
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Jan Kiszka <jan.kiszka@siemens.com>, QEMU Developers <qemu-devel@nongnu.org>, "Michael S. Tsirkin" <mst@redhat.com>

On Mon, 2013-09-09 at 14:02 +0100, Peter Maydell wrote:
> On 9 September 2013 13:59, Michael S. Tsirkin <mst@redhat.com> wrote:
> > On Mon, Sep 09, 2013 at 01:52:11PM +0100, Peter Maydell wrote:
> >> It would be conceptually nicer not to treat host bridges as
> >> a special case but instead to just report the abort back
> >> to whatever the PCI master was (which might be a device
> >> doing DMA). That might be a lot of effort though.
> 
> > Yes. As a shortcut, what I suggest is registering the
> > device that wants to be notified of master aborts with
> > the bus.
> 
> Can you just pick the device which is (a subclass of)
> TYPE_PCI_HOST_BRIDGE, or do we have host bridges which
> aren't using that class?
This is what I would really want to do, but some HOST Bridge devices
inherit directly from PCI_DEVICE.

TYPE_PCI_HOST_BRIDGE derives from TYPE_SYS_BUS_DEVICE which
is a not a PCI device and does not help us here (not a PCI_DEVICE
on the bus)

Strangely TYPE_Q35_HOST_DEVICE derives from TYPE_SYS_BUS_DEVICE
and it hold as composition a PCIDevice that will be part of
the bus, as opposed to TYPE_I440FX_PCI_DEVICE which directly
inherits from PCI_DEVICE.

It seems to me as a dead end, or we need to re-factor the current
hierarchy.

Marcel
> 
> -- PMM