Re: [Qemu-devel] [Qemu-ppc] [PATCH v2] pci: allow 0 address for PCI IO/MEM regions

[Michael Roth <mdroth@linux.vnet.ibm.com>]

Quoting Peter Maydell (2015-07-23 16:24:20)
> On 23 July 2015 at 22:19, Peter Maydell <peter.maydell@linaro.org> wrote:
> > On 23 July 2015 at 22:10, Michael S. Tsirkin <mst@redhat.com> wrote:
> >> On Thu, Jul 23, 2015 at 10:00:30PM +0100, Peter Maydell wrote:
> >>> (Also, none of our PCI device models actually try to do
> >>> the "BAR at zero means I won't respond" behaviour, which
> >>> presumably they might do in real life.)
> >
> >> Maybe some devices do this, but I'm guessing not all of them,
> >> since there's no hint in the pci spec that they should.
> >
> > I think this depends on which version of the spec you
> > read.
> 
> Bikeshedding about ancient specs aside, I think it's the
> bugs in the PC model's memory region priorities that
> are the real reason the special case of zero is sticking
> around. If we fixed those we should be able to drop it.

What's the intended fix? That legacy/platform regions
should hide any regions a guest attempts to map over it?

> 
> -- PMM
>