Re: [Qemu-devel] [PATCH v1 5/5] hw/arm: Add the Netduino Plus 2

[Peter Maydell]

On Tue, 30 Apr 2019 at 21:29, Alistair Francis <address@hidden> wrote:
>
> On Tue, Apr 30, 2019 at 9:02 AM Peter Maydell <address@hidden> wrote:
> > Can you explain the purpose of the reset code? None of the other
> > v7m boards seem to need to do a manual qemu_register_reset().
>
> The reset code allows the machine to work with the -kernel option.
> Without the reset override using -kernel results in the guest starting
> at the wrong address. We can use the -device loader option without the
> reset code though.

That sounds in line with how -kernel works on the other armv7m
boards -- the expectation is that your image file includes a
full vector table and the CPU will read the PC and SP from it
when it resets. If you want "honour the entry point" you can
use -device loader, as you say.

Ignoring the entry point for -kernel ELF files is certainly
a bit confusing, but I think if we want to change this we should
do it globally, rather than having one board which behaves
differently to the rest. Changing it does have some awkwardness:
 * possibility of breaking previously working images
 * we can get the initial PC from the ELF entrypoint, but if
   we do this what do we do about the initial SP value ?

thanks
-- PMM