Re: [Qemu-ppc] Problem booting qemu-system-ppc with cpu e500XX and machine mpc8544ds

[Scott Wood]

On 07/03/2012 12:22 AM, Badrinath Sriman wrote:
> I am using the bootable CDROM option only because qemu requires the
> CDROM/hard disk images to be bootable. On real hardware, we use the
> bootm option of U-boot. Using qemu, I was not able to find helpful
> instructions to boot netbsd/ppc via. uboot (as bootloader).

U-Boot doesn't run in QEMU -- it would require a lot more hardware to be
emulated and/or changes to U-Boot.

> The
> nearest that I could come to booting netbsd/ppc combination was
> through ofwboot as the bootloader.

That's not going to work without an Open Firmware implementation, which
we don't have on e500 either in QEMU or on real hardware. :-)

> I am now trying to use the -kernel
> option to boot the netbsd kernel. Looks like the -M mpc8544ds option
> mandatorily requires a FDT. The netbsd that we are using does not
> have the FDT option when it is compiled. So trying to understand more
> about FDT and the qemu implementation of FDT, to debug the booting
> issue.

QEMU will pass an FDT to the target, but the target doesn't need to use
it.  The FDT comes from QEMU -- it used to be in pc-bios/, but on
top-of-tree it is now generated internally to QEMU and doesn't need to
be passed in on the command line anymore.

However, a problem with the target OS not being device tree driven is
that QEMU doesn't emulate all the hardware on a real mpc8544ds.  It
emulates a small subset, and the device tree is how this subset is
communicated.  So you'll have to somehow make sure that NetBSD is not
trying to access any devices other than the one serial port, the one PCI
bus, and the reset register in the global utilities block.

-Scott