Re: Booting on QEMU

On Tue, Oct 26, 2021 at 01:30:31PM +0200, BALATON Zoltan wrote:
> The current 9.2 version is not affected and still boots before and after but
> older versions which booted without this change now get strange errors as
> reported in the above OpenBIOS list thread. Any idea what may be wrong or how to
> debug it further?

The memory disk root file system, which for this kernel is embedded
into the kernel data section, is corrupt.

So either something goes horribly wrong when reading the kernel from the
boot medium (ofwboot.xcf does that using OF callbacks, so very unlikely),
or the new OF node makes the kernel code corrupt some memory post-loading.

I don't remember related fixes (nor see any in the CHANGES-9.2 file), so maybe
it is just pure luck that 9.2 boots (because the corruption hits in a different
location).

Would it help if we print the memory range where the MD image lives
early and you could use qemu tracing to catch any writes to that range
afterwards? The range is probably constant for consecutive boots with
the same args and the MD file system should still be read-only at the
point where it crashes for you.

Martin