Re: qemu platform patches

	
On Aug 18, 2008, at 9:17 PM, Miklos Vajna wrote:

Hi!

I recently started to search for a solution to boot a Linux-2.6-based
kernel in qemu-system-ppc.

Google found two of your interesting patches:
http://patchwork.ozlabs.org/linuxppc/patchcontent?id=13689
http://patchwork.ozlabs.org/linuxppc/patchcontent?id=13690

...

Sadly the build fails at your qemu.c, with:

  BOOTCC  arch/powerpc/boot/qemu.o
arch/powerpc/boot/qemu.c: In function 'tree_fixups':
arch/powerpc/boot/qemu.c:203: warning: implicit declaration of function 'dt_find_initrd'
arch/powerpc/boot/qemu.c: In function 'platform_init':
arch/powerpc/boot/qemu.c:230: error: 'struct platform_ops' has no member named 'find_vmlinuz'
make[1]: *** [arch/powerpc/boot/qemu.o] Error 1
make: *** [zImage] Error 2

Two questions:

1) Do you remember what was the exact commit you worked with, where
qemu.c compiled fine? (In case you have newer patches somewhere, I'm
interested as well :) )

From those messages, there were other patches posted about the same time that did some radical splits to the zImage infrastructure code, allowing it to become a helper instead of just a contained image.

And I do have later patches that were working (better).  I have even booted a linux-next kernel just before 2.6.27 opened, after doing some fixups.  However, I suffer from wanting to perferct the function of the patches and never get the base part out :-).  For instance, when working with 2.6.27, I got ISA memory working and some video output.  Also, the ide-generic driver now has to be enabled on the command line to give the same function we previously had.  That, combined with kernel for ppc-qemu is my hobby and my work keeps interrupting me.

The current state is: Rob Landley's Firmware Linux has a ppc_rom.bin (and source) written by me that probes qemu nvram for the size of memory, location of a command line (-append) and initrd (-initrd), patching a device tree linked into it, then parses the kernel (or other elf file) loaded via -elf a kernel and jumps into it whereever it was loaded.  The kernel has a corresponding platform patch that only recognises qemu (based on the kernel patch you found).  The version Rob has works on 2.6.25.9 with serial, ide, and isa ne2000.  Since then I got isa memory to enable video (with hacks and you only see 1/4 of the screen).

http://landley.net/hg/firmware/raw-file/6f1e69d7e7f5/sources/toys/make-ppc_rom.tar.bz2
http://landley.net/hg/firmware/raw-file/59e22ea53e6a/sources/patches/linux-ppcqemu.patch
http://landley.net/hg/firmware/raw-file/0d8e80202e94/sources/patches/linux-2.6.23-ppcne2khack.patch

2) I'm not exactly sure about the build process in the case of qemu,
using your patches.

Am I right about I just have to compile the kernel, I'll be given a
ppc_rom.bin and the usual vmlinux file, then I can boot these with qemu?

The version that you have built a rom out of the code in arch/powerpc/boot after patching.  The new version builds the rom in a shell script.   Either way, it activated by calling it ppc_rom.bin and pointing QEMU's library drectory to it with the -L flag.  This code works for qemu -kernel when the kernel is patched to recogonise the qemu platform specified in the device-tree.

Going forward, it probably needs to become a dtbImage or a combination rom and optional image.

Hopefully the rest is clear, currently I have 2.4.36.1 in qemu and it
would be really time to upgrade to 2.6 :)

People were successfully able to get arch/ppc kernel to boot as last ase 2.6.26, at least until they got to userspace.  That doesn't provide a way forward, as ppc is now removed, but it may provide a temporary option.

I can't promise a timeframe, but I do want to get the patches updated and out.

milton