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

[Peter Maydell]

On 30 September 2015 at 21:17, Max Filippov <address@hidden> wrote:
> On Tue, Sep 29, 2015 at 11:42 PM, Peter Maydell
> <address@hidden> wrote:
>> On 29 September 2015 at 11:34, Max Filippov <address@hidden> wrote:
>>> Changing address space layout according to CPU type is what happens
>>> in actual hardware. There are no user-controllable settings that would
>>> allow mismatching address space layout and CPU type on XTFPGA
>>> boards. There's also no SoC level mentioned in the developer guides
>>> for the corresponding boards. So I'm not sure what you're proposing to do.
>>
>> I think this should clearly be different machine models
>> (possibly implemented using different SoC models).
>
> There are already 4 different machine models, lx60, lx200, ml605 and
> kc705, these are real boards for which bitstreams can be created.
>
>> This isn't a
>> CPU-dependent thing at all, it's just your dev tools are hiding
>> "change the devices and other board/soc level things" behind a
>> CPU-type dropdown, which it can get away with because the whole
>> implementation is in a single FPGA.
>
> Why duplicating each machine and then only allowing each CPU to be
> used with only one variant of each machine? It doesn't match what
> users do with boards and bitstreams, at all.

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.

thanks
-- PMM