Re: [Qemu-devel] [RFC PATCH 10/10] hw/pci-host/gt64120: Clean the decoded address space

[Paul Burton]

Hi Philippe,

Sorry for the delay; I was away for a few weeks visiting family.

On Mon, Jul 01, 2019 at 08:06:21PM +0200, Philippe Mathieu-Daudé wrote:
> The difference with the previous content is now we have
> two new holes:
> 
> - 0x02000000-0x10000000
> - 0x14001000-0x1c000000
> 
> Ralf/Paul/James, what should happen when a guest access these
> holes (hardware PoV, no QEMU)?

I don't have a Malta handy to check (they're mostly "retired" these
days & the vast majority of surviving ones use newer FPGA daughtercards
with the MSC01-style system controller anyway), but I believe writes
just get dropped & reads return zero. At least that's the way I recall
most accesses to unused address ranges working on Malta.

(Which is really annoying sometimes, and the newer Boston system gives
you a bus error in the equivalent scenario.)

Thanks,
    Paul