On 10/8/21 4:01 pm, Gerd Hoffmann wrote:

Hi,

insmod /lib/modules/5.13.8/kernel/fs/jbd2/jbd2.ko
insmod /lib/modules/5.13.8/kernel/fs/mbcache.ko
insmod /lib/modules/5.13.8/kernel/fs/ext4/ext4.ko
mount: mounting /dev/sda2 on /mnt failed: No such file or directory
ERROR: No /sbin/init found on rootdev (or not mounted). Trouble ahead.
You can try to fix it. Type 'exit' when things are done.

At that point I'm dropped into a recovery shell to try fixing something
but there's nothing that can be done since the disk containing the OS is
not visible.

From the above, I think I've done everything possible to verify the
problem and a possible fix. Is there something fundamentally wrong in
the way I'm going about this?

Root cause is not clear. Grab the kernel log ('dmesg') from a good and
a bad boot and comparing them should give a clue.

Thanks for your interest Gerd,

I added "-serial mon:stdio" to the qemu invocation and "console=ttyS0"
to the -append line to capture all boot output for both good and bad
cases and saved the results in files.

Rather than spam the list with those outputs, I've added them as
attachments to the bz report at
https://bugzilla.tianocore.org/show_bug.cgi?id=3504

When I first diff'd them, the slight difference in time stamps meant
every line showed up as different - real differences were hard to see.
Therefore I amended the files to replace the time stamps with "xxxx",
enabling diff to show actual differences more meaningfully.

I also attached there the output of a diff between the bad & good cases.
To be honest I can't see anything striking to explain the difference in
behaviour. To me, the main difference is that in the good case, an QEMU
HARDDISK & QEMU DVD-ROM are discovered and allows the system to boot but
no obvious indication why they are discovered in one case but not the
other. Apart from that, there are a few differences in some memory
locations being used but I have insufficient knowledge to judge whether
those differences are significant.

Is it possible for anyone to have a quick look through those files for
anything that may indicate what is causing the defective booting please?

Thanks,
chris