Re: Changing bootstrap method for NewWorld Power Macs
On 31/12/2018 13:15, Frank Scheiner wrote:
> Hi Mark,
>
> On 12/31/18 00:49, Mark Cave-Ayland wrote:
>> On 30/12/2018 21:01, Frank Scheiner wrote:
>>> Open Firmware (IEEE 1275) can actually also boot from FAT file systems and this is
>>> also supported on NewWorld Power Macs.
>>
>> Unfortunately not everyone uses Open Firmware, and in particular OpenBIOS provided
>> with QEMU doesn't currently support FAT filesystems. So as the QEMU macppc maintainer
>> this change would then immediately cause the latest Debian images to fail to boot,
>> which is not something I can get excited about.
>
> Sorry to hear that, though I think you need to provide additional details at this time:
>
> What do you mean with "Debian images"? Because if you speak of the installer ISOs, my
> changes won't change anything with their ability to boot on NewWorld Power Macs or
> QEMU (I think).
The part I'm worried about is that OpenBIOS searches the Apple Partition Map for an
"Apple_Bootstrap" partition on PPC Mac machines, probes the FS, and then tries to
boot dev:part:,\\:tbxi, dev:part:,\ppc\bootinfo.txt and dev:part:,%BOOT in that order.
I believe that yaboot blesses itself on the HFS "Apple_Bootstrap" partition which
allows OpenBIOS to locate and run the bootloader. My understanding is that you would
like to change to MBR and FAT16 which would then fail in QEMU as OpenBIOS doesn't
have a functioning FAT driver - is that correct?
> My changes also do not remove existing code related to HFS as bootstrap. I expect
> that you will be able to still create all relevant partitioning and file systems
> manually from within the Debian installer, if needed to make it work under QEMU.
>
> Please also realize that the original idea was to support GRUB installations on
> NewWorld Power Macs, something that doesn't work (automatically from the Debian
> installer) at the moment. To be completely honest, if we no longer need to depend on
> specific non-generic code, at the same time, I won't reject that.
>
> Other point: why can't you directly load kernel and initramfs with QEMU?
That is one potential workaround, but for years everyone has booted their PPC VMs
under QEMU with "qemu-system-ppc -cdrom path/to/cdrom.iso" and for me that is an
extremely high barrier, particularly for novice users, to require them to extract a
kernel and initrd from an ISO first.
ATB,
Mark.
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