KVM: PPC: Book3E: KVM HV host module doesn't work anymore

[Paolo Bonzini]

On Sun, Dec 22, 2024 at 5:24 PM Christian Zigotzky
<chzigotzky at xenosoft.de> wrote:
> Hello Paolo,
>
> I tried it but there is a host boot issue at the same time. Bisect log:
> https://github.com/chzigotzky/kernels/issues/4

Thanks, I left there some instructions which I'll copy here for reference.

We need to bisect the host boot issue:

  git bisect start
  git checkout c9be85dabb376299504e0d391d15662c0edf8273
  # check that it does not boot
  git bisect bad
  git checkout adc218676eef25575469234709c2d87185ca223a
  # check that it boots
  git bisect good

If the two commits have the expected result, the first bisection step should be

  # Bisecting: a merge base must be tested
  # [e9001a382fa2c25...] Merge tag 'kvmarm-fixes-6.12-3' of ...

There are two possibilities.

## If e9001a382fa2c25 succeeds to boot ##

Then `git bisect good` and bisect to the patch that causes the host to
fail to boot. What's left seems to be all non-PPC KVM patches, which
is a bit weird but you never know. Once you have the result, we'll try
to fix that, and provide you with a fixed branch to bisect the actual
KVM-PPC failure.

A potential candidate, based on your skips, is commit eec1e5db464e
("KVM: Annotate that all paths in hva_to_pfn() might sleep").

Please also provide the messages for the boot failure (I haven't seen
it but I might be missing it).

## If e9001a382fa2c25 fails to boot ##

Then the boot regression was in the v6.12 tree. Fortunately the KVM
tree can be rebased without conflicts to v6.12; go on with

```
git checkout -b bisection-rebase b467ab82a9fde4b46c0cd2c299220857afb0e0d4
git rebase v6.12
# check that it boots. if it fails to boot, please report this. if it
succeds, continue:
git bisect start
git bisect bad bisection-rebase
git bisect good v6.12
```

Proceed to bisect looking for the failure to start guests. If you
never find a kernel that fails to boot, report the bisection log.

If you find a kernel that fails to boot, drop the bisection. Start
another bisection between v6.12 and bisection-rebase, this time
looking for the first patch that fails to boot, and report the
bisection log + the boot failure messages.

Paolo