Re: [Qemu-devel] [PATCH RFC 3/3] hw/pci-host: catch acesses to unassigned pci addresses

[Michael S. Tsirkin]

On Mon, Sep 02, 2013 at 05:05:10PM +0100, Peter Maydell wrote:
> On 2 September 2013 17:00, Michael S. Tsirkin <address@hidden> wrote:
> > On Mon, Sep 02, 2013 at 04:53:50PM +0100, Peter Maydell wrote:
> >> at the moment what happens is that the pci controller
> >> creates the PCI memory and io memory regions (or cheats
> >> by reusing the system memory space[*]),
> 
> >> [*] I'm pretty sure this is a bug in all platforms that do it.
> 
> > Well as usual this cheat originated with PIIX.
> > AFAIK PIIX actually has a shared bus for memory and PCI
> > so this is not a bug there, I think.
> 
> It will be when you introduce this "return -1 for unassigned
> addresses", though, since you only want that to happen
> for PCI accesses, not system memory accesses, right?
> 
> thanks
> -- PMM

What happens with PIIX is that everything that is not
in system memory is PCI.
So there's no such thing as "unassigned system memory
address": all unassigned addresses are PCI addresses.

-- 
MST