Re: [Qemu-devel] [PATCH v1 1/1] target_arm: Make the reset rom_ptr a property

[Peter Maydell]

On 21 August 2014 13:09, Alistair Francis <address@hidden> wrote:
> On Thu, Aug 21, 2014 at 7:14 PM, Peter Maydell <address@hidden> wrote:
>> This isn't making a great deal of sense to me. If you
>> mean that the board design allows some sort of
>> programmable or configurable remapping of the
>> address space, we should implement that by
>> mapping and remapping MemoryRegions into place
>> as appropriate, not by messing with the CPU reset.
>
> This is the one that I mean.
>
> Either Main Flash, System Flash, FSMC Bank1 or SRAM
> are mapped to address 0 based on the value of a register.
>
> This is checked after reset or when the device exits standby.
>
> If trying to run any code on QEMU, it will immediately error with
> executing code out of memory at address 0 (if compiled without
> this change). What do you think would be the best method to
> implement this in QEMU?

You need to model the behaviour of the board in the
QEMU machine model, so that the right kind of
thing appears at address zero. It doesn't sound like
you need to change the behaviour of the CPU emulation
at all, because reading the PC and SP from 0 is the
correct behaviour.

Since we don't support this board upstream I assume
you're talking about some out-of-tree board model, so
it's a bit difficult to give exact suggestions.

Does the guest code actually make use of the dynamic
remapping, or is it sufficient to implement your board
as "always flash at 0" or "always RAM at 0" ?

thanks
-- PMM