[Qemu-devel] PreP kernels boot using Qemu

["J. Mayer" <l_indien@magic.fr>]

Hi all,

I've been investigating more about PreP kernel boot using Qemu and I
achieved to boot 2.4.35, 2.6.12 and 2.6.22 kernels using Qemu CVS and
unmodified OHW.
The issues I found in the kernel are:
- the OpenFirmware video console driver is broken in recent 2.4 kernels
and have been removed from recent 2.6 kernel
- I then decided to use the vga16fb console driver but needed to do some
patches in order to make it compile properly
- the CMOS RTC driver is not available for PPC architecture in 2.6
kernels and need some patches in order to be usable
- I discovered that the mkprep utility is bugged in 2.4.35 and 2.6.12
kernels. The bugs are visible only when cross-compiling from a
little-endian and/or 64 bits host.
- I got issues (ie process freezing) when using the 2.6.22 kernel with
HZ > 100. It seems to run properly when the system timer is set to 100
Hz but this needs more tests for confirmation.
- I got the 2.6.22 kernel crashing (ie kernel Oops in workqueue code)
when it has no RTC available. There is no problem when the RTC is
present. This is likely to be a kernel bug: when no RTC is available, it
cannot calibrate its timers properly and the kernel timer seems to run
very fast. Forcing (with hacks...) the timer to run at nearly real-time
seems to prevent the bug to happen.

I then generated some kernels that allow me to boot and use those 3
kernels.
Here are 3 tarballs with:
- a patch to be applied to the vanilla kernel sources to fix the
mentionned bugs
- the .config file I used to build the kernel
- the zImage.prep image
<http://perso.magic.fr/l_indien/qemu-ppc/linux-tests/linux-2.4.35-prep.tar.bz2>
<http://perso.magic.fr/l_indien/qemu-ppc/linux-tests/linux-2.6.12-prep.tar.bz2>
<http://perso.magic.fr/l_indien/qemu-ppc/linux-tests/linux-2.6.22-prep.tar.bz2>

I then run Qemu with the following command line template:
./ppc-softmmu/qemu-system-ppc -serial stdio -net nic,model=ne2k_isa -net
tap -net nic,model=ne2k_pci -net tap -net nic,model=rtl8139 -net tap
-cpu 604 -M prep -L pc-bios/ -hda <my_first_disk> -cdrom <my_cdrom>
-kernel
<src_base>/linux-<kversion>.patched/arch/ppc/boot/images/zImage.prep

Hope this helps.

-- 
J. Mayer <l_indien@magic.fr>
Never organized