Re: [Qemu-ppc] [Qemu-devel] [PATCH 08/12] pci: allow 0 address for PCI IO regions

[Michael S. Tsirkin]

On Thu, Aug 28, 2014 at 10:33:02PM +0100, Peter Maydell wrote:
> On 28 August 2014 22:21, Michael Roth <address@hidden> wrote:
> > But I guess there's still a separate issue, where there's a high liklihood 
> > that
> > a 0 address would conflict with some hard-wired IO address? Wouldn't this 
> > be a
> > guest bug though?

Real hardware behaves in a specific way.
the problem is we don't always emulate it properly, and PCI
has some work arounds for that.

> Even if it's a guest bug, we should act like the hardware does
> if the guest does this. If that differs between PCI controllers
> then we need a flag so the host controller model can select
> the required behaviour. (The versatile PB PCI controller we
> model does have "address 0 is valid", and we'd need to have
> this working if we implemented DMA accesses properly.)
> 
> -- PMM

Exactly.
Actually, I forgot that I might have already fixed it for PC:
83d08f2673504a299194dcac1657a13754b5932a
    pc: map PCI address space as catchall region for not mapped addresses

But need to go back and re-check other systems.


-- 
MST