Re: [Qemu-devel] Better Cortex-M support?

[Liviu Ionescu]

On 12 Nov 2014, at 15:02, Peter Maydell <address@hidden> wrote:

> The instructions themselves are generally supported for
> the A profile cores, so getting that part right would mostly
> involve enabling those feature bits for the new M4 CPU class.

ok

> The difficult bits are going to involve:
> * correct trapping when fp is disabled
> * getting the exception handling right, including lazy
>   exception frame population
> * bits where M profile FP differs from A profile (eg fp
>   status and ID registers being memory mapped)

all seem related to FP, which, for my priority list, comes second, after 
specific vendor system registers for the supported processors.

my first priority is to make the emulator run the images generated by the 
project templates *without* any changes.

this requires the presence of the registers used by the CMSIS SystemInit() 
call, which generally are vendor specific, related to clock settings (pll & co).

> For upstream we would just want to fix arm-softmmu, I think.

for me, the plain arm-softmmu is not usable, since it forwards the semihosting 
calls via gdb instead of using native implementation, so I had to add a 
configuration variable to change this behaviour.

> For submitting changes upstream you'll need to clean up
> this set of commits (rebase, rearrange, split or merge commits,
> etc so you have one commit (patch) per thing you're fixing and
> it's a clean change that stands on its own.

I understand. I'll consider this, but we'll probably postpone until significant 
improvements are there and someone else needs them.


regards,

Liviu