[Bug 203837] Booting kernel under KVM immediately freezes host

[Nicholas Piggin]

bugzilla-daemon at bugzilla.kernel.org's on June 7, 2019 4:29 pm:
> https://bugzilla.kernel.org/show_bug.cgi?id=203837
> 
> --- Comment #2 from Paul Mackerras (paulus at ozlabs.org) ---
> Just tried 5.1.7 in the host and got the guest locking up during boot. In xmon
> I see one cpu in pmdp_invalidate and another in handle_mm_fault. It seems very
> possible this is the bug that Nick Piggin's recent patch series fixes
> ("powerpc/64s: Fix THP PMD collapse serialisation"):
> 
> http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=112348

It's worth a try, although the bug was introduced around 4.20 and
I wasn't able to trigger it on radix, but other timing changes
could cause it to trigger I suppose.

pdbg (https://github.com/open-power/pdbg) is a useful tool for your
BMC that can often get the CPU registers out even for bad crashes,
this might help to narrow down the problem without bisecting.

Thanks,
Nick