Re: [Qemu-ppc] VxWorks 5.5.1 on qemu powerpc

[Alexander Graf]

On 04/01/2014 11:04 AM, FOURNIER Maxime wrote:
> Hi,
>
> We're currently seeking to run VxWorks 5.5.1 on qemu-system-ppc
> and we do not manage to make it boot.
>
> To put the context: we did manage to do so on qemu-system-x86 and
> we're just studying if it's possible or not on qemu powerpc.
>
> The targeted cpu is a powerpc 604.
>
>
>
> Considering some documentation and what has been said on several
> mailing lists we assume that:
> - -kernel argument stands for a linux kernel.
>    VxWorks doesn't end up happy with it. (-bios doesn't change anything).
>
> - Qemu may be unable to launch anything else than
>        a linux kernel (and some other specific Oses we're not interested in).
>
> We've seen that:
> -   The prep open hack'ware bios continuously says it doesn't find any
>      bootable prep partition (We created a disk image with fdisk
>      and code 41 + boot flag).
> -   The open bios manages to load the binary but the boot sequence fails
>      (no execution at all (cpu_exit)).
> -   There are no compatibles bsps between VxWorks and qemu
>      emulated boards/platforms.
> For that we may start developing of a new board (nothing sure yet).
>
> We've tried some solutions:
> - Cross compile and run grub 2, u-boot so we can specify a payload and then
>      jump at the kernel start point.
>      - Grub 2 starts and freezes with default platform (openbios).
>      - U-boot doesn't start (default, prep, mac99 platform).
> - Patching all addresses in qemu source code (we do manage to call the binary
>      and jump at the correct execution address (0x00100000)). Still,
>      nothing happens.
> - Switch bios or crosscut bios to load kernel directly, still doesn't work.
>
> We know that the kernel starts on the e500 platform but freezes because of
> an access to a 604 specific register (spr 532 IBAT2U).
>
> A patch has been submitted to run a payload such as u-boot on the e500
> platform. (we haven't tested it yet).
>
> Unfortunately we do not want an e500 card, but the standard prep platform
> may offer the less incompatible solution with VxWorks for a start.
>
> As there is currently no compatible board except the walnut (that was submitted
> as a patch but apparently never made it to the official sources) we know it
> will not go far.
>
> So for now we just want to start the kernel and let it crash at some point.
>
>
>
> Did someone managed to make this OS boot on qemu-powerpc ?

Yes, Fabien Chouteau had VxWorks running on e500 IIRC.

> Did we miss something or did we make wrong assumptions ?
>
> What are the main differences between the e500 and the prep platform booting
> procedure (so we can try to figure out why it is starting on e500 and not on
> prep) ?

You can check in the board file. The main difference today is that the 
e500 machine loads the -kernel blob directly and jumps to it first thing 
while the "desktop class" platforms load a firmware blob which then 
bootstraps into the kernel.

> Do you need any particular data or further testing ?

I'm not sure what you're expecting to happen. If you take your VxWorks 
image and put it into a real PReP machine, does it work? If not, why 
would it work in QEMU? If you take a real Apple Mac and try to run 
VxWorks there, does it boot? If not, why should it boot in QEMU's model 
of that machine?

What exactly are you trying to do? Are you trying to run a VxWorks build 
for a specific target system? Then you probably need to start 
implementing that model. If you only want any VxWorks PPC build work, 
why not leverage Fabien's work?


Alex