Re: [Qemu-devel] [PATCH 3/3] target-xtensa: xtfpga: support noMMU cores

[Peter Crosthwaite]

On Wed, Sep 30, 2015 at 3:23 PM, Peter Crosthwaite
<address@hidden> wrote:
> On Wed, Sep 30, 2015 at 3:07 PM, Max Filippov <address@hidden> wrote:
>> On Thu, Oct 1, 2015 at 12:02 AM, Peter Crosthwaite
>> <address@hidden> wrote:
>>> On Wed, Sep 30, 2015 at 1:54 PM, Max Filippov <address@hidden> wrote:
>>>> On Wed, Sep 30, 2015 at 11:45 PM, Peter Maydell
>>>> <address@hidden> wrote:
>>>>> Because for QEMU the CPU is really just the CPU. Your other
>>>>> random devices don't live in the CPU, even if you're
>>>>> programming your FPGA with a single bitstream that's
>>>>> got the CPUs and a set of devices in it. You can't push
>>>>> that stuff into the CPU model, it should live in the
>>>>> board model.
>>>>
>>>> I'm not pushing them into CPU model and they do live in the board
>>>> model. After all the changes in question were for the hw/xtensa/xtfpga.c
>>>> But the board is made in such way that CPUs with and without MMU
>>>> see onboard RAM and peripherals at different physical addresses.
>>>
>>> Which makes MMU vs noMMU a board level property, not a CPU property.
>>> It should appear in QEMU as such.
>>
>> Ok, one last try: can this property be queried from the selected CPU
>> and passed to SoC initialization code?
>>
>
> No, what I am trying to say is go the other way round. The property is
> on the SoC, and it is used to select the CPU type.
>

Another thought that may help/clarify. Maybe xtfpga, or a lot of it's
content belongs as an object in hw/cpu/. Its not a CPU (QEMU
terminology), but it's not a board either, it is something inbetween.
There are two concepts in the ARM world, that are in the middle, SoC's
and MPCores. MPCores live in hw/cpu/. Some notes.

* the fact that ARM boards still create the CPUs on the side of MPU
cores is a design issue I am trying to fix.
* ARMs virt machine using CPU type to select MPCore is a legacy.

Regards,
Peter

> Regards,
> Peter
>
>> --
>> Thanks.
>> -- Max