Re: [Qemu-devel] Loading image/elf to cpu that has different not system memory address space

[Peter Crosthwaite]

On Wed, Sep 23, 2015 at 10:31 AM, mar.krzeminski
<address@hidden> wrote:
> W dniu 23.09.2015 o 17:46, Peter Maydell pisze:
>
>> On 23 September 2015 at 08:17, Marcin Krzemiński
>> <address@hidden> wrote:
>>>
>>> Hello,
>>>
>>> I am trying to write a model of embedded board that have corterx-m3 and
>>> cotex a9 processors.
>>> Because M3 see different memory at address 0x0 than A9 (m3 has small rom,
>>> a9
>>> has whole ram) I created different address space for m3 (thanks Peter
>>> Crosthwaite! for hints how to do this!).
>>> Now I stacked at loading "kernel" to start M3. If I use default address
>>> space for M3 I can load I run my elf filr (it can be image, but currently
>>> it
>>> is easiest for me with elf) all works fine.
>>> The problem is when I switch to my new (root MR is not from
>>> get_system_memory() call ) i got execution outside RAM exception.
>>> That is happening because there are only zeroes in memory pointed by my
>>> second address space.
>>> The question is how can I load image to this memory (it might be elf, but
>>> binary image also is fine)?
>>> I can not even find the code that loads data to memory in fist place.
>>> Could
>>> you point me where the loading is done in the code?
>>
>> This is going to be complicated. I suspect you will need to add
>> some infrastructure for specifying per-CPU image loading (maybe
>> via CPU properties?), which we don't have at all right now.
>>
>> (Our current image loading code for arm lives in hw/arm/boot.c.)
>>
>> thanks
>> -- PMM
>>
> I couldn't find the place were actual data are put int M-, I don't know why
> I haven't seen
> rom_add_blob() in boot.c.
> At the machine init level I know all MRs, so I'll use
> memory_region_get_ram_ptr(),
> and put data there.
> If you have idea how to add this into framework, and someone beside me needs
> this,
> maybe I can implement that?
>

We definately need it. We need to be able to associate multiple
softwares with multiple CPUs.

This is known to work, and could be what you are looking for:

https://github.com/Xilinx/qemu/blob/pub/2015.2.plnx/hw/misc/blob-loader.c

You pass -device loader,cpu=#,...

then various other fields, all on the command line (depending if your
loading elfs or raw blobs). It is badly named, it is more than just a
blob loader now. It works best when you don't use -kernel (you may
need to hack your machine model to disable any checks that forces
-kernel).

The key feature of that device is it loads from the argument CPUs
perspective, so if your M3 CPU AR is correctly set it will load via it
when you use -device loader,cpu=1,foo.elf.

The implementation is slightly bogus, it is using a global AS pointer
loader_as to pass the cpu AS to loader infrastucture. git grep that
tree (2015.2.plnx branch) for "loader_as" to see the needed changes to
core loader infrastructure and cherry pick the device and it should be
close to working.

HTH

Regards,
Peter

> Thanks,
> Marcin