Re: [Qemu-devel] [PATCH 1/2] memory: Provide separate handling of unassigned io ports accesses

[Jan Kiszka <jan.kiszka@web.de>]

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On 2013-08-05 12:51, Peter Maydell wrote:
> On 5 August 2013 11:44, Jan Kiszka <jan.kiszka@web.de> wrote:
>> On 2013-08-05 12:36, Peter Maydell wrote:
>>> On 5 August 2013 11:30, Jan Kiszka <jan.kiszka@web.de> wrote:
>>>> On 2013-08-05 11:59, Peter Maydell wrote:
>>>>> Or do you mean that if we had:
>>>>>
>>>>>  [ system memory region, with its own default read/write ops ]
>>>>
>>>> I cannot imagine how this could work. The system memory region has no
>>>> clue about what the regions below it can handle and what not. So it has
>>>> to pass through the io window.
>>>
>>> The system memory region's just a container, you can add a
>>> background region to it at lowest-possible-priority, which
>>> then takes accesses which are either (a) not in any subregion
>>> or (b) in a subregion but that container doesn't specify
>>> its own io ops and nothing in that container handles the
>>> access. (Or you could create the system memory region with
>>> its own IO ops, which would have the same effect.)
>>
>> First, we do not render MMIO and IO within the same address space so
>> far.
> 
> Is this a statement made because you've checked all the boards
> and know that nobody's mapping the system-io memory region into
> the system-memory region? (It is technically trivial, you
> just need to call memory_region_add_subregion() directly
> or indirectly...)

I know this because I just recently wrote the patch that enables this
trivial step, i.e. converted PIO dispatching to the memory subsystem.

Jan



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