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

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

Quoting Michael Roth (2015-07-23 16:38:19)
> 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?

nm, i see this was already covered :)

I seem to recall Michael suggesting it may have already been
fixed on x86. I think we had a TODO to figure out all
the architectures that don't use IO windows and figure out
if they need a fix as well.

> 
> > 
> > -- PMM
> > 
> 
>