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From: Alistair Francis <alistair23@gmail.com>
Date: Tue, 2 Sep 2014 11:55:22 +1000
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Subject: Re: [Qemu-devel] [PATCH v1 0/5] Netduino Plus 2 Machine Model
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Peter Crosthwaite <peter.crosthwaite@xilinx.com>, QEMU Developers <qemu-devel@nongnu.org>, Konstanty Bialkowski <konstanty@ieee.org>

On Tue, Sep 2, 2014 at 2:39 AM, Peter Maydell <peter.maydell@linaro.org> wrote:
> On 24 August 2014 01:13, Alistair Francis <alistair23@gmail.com> wrote:
>> The Netduino Plus 2 has a Cortex-M4 in it, while this model uses
>> a Cortex-M3 as that is supported by QEMU. This means that the code
>> that runs on the Netduino Plus 2 is recompiled for a Cortex-M3 with
>> out Floating Point or DSP optimisations.
>>
>> For my use of this it doesn't matter if the code has to be recompiled,
>> so I have no desire to add support for the Cortex-M4.
>
> That does make things a bit awkward. I don't really want to
> add something that claims to be a model of board X if in
> fact it won't run anything that isn't specifically built for
> "QEMU's deficient model of board X". It seems to me that
> would just be a recipe for lots of user complaints...

So the only way you would take this machine is with Cortex-M4 support?
I agree it is a bit awkward, but at the moment it is the best I have. I am going
to look into the Netduino 2 as well, as that uses a Cortex-M3, but I'm not sure
how similar everything else is.

It's my understanding that the FPU in the Cortex-M4 is optional (as in not
every M4 has it). Does this mean that the only differences between a M3 and M4
in QEMU would be registers and instructions for DSP?

Thanks,

Alistair

>
> thanks
> -- PMM