Injecting SLB miltihit crashes kernel 5.9.0-rc5

[Nicholas Piggin]

Excerpts from Michael Ellerman's message of September 15, 2020 10:54 pm:
> Michal Suchánek <msuchanek at suse.de> writes:
>> Hello,
>>
>> Using the SLB mutihit injection test module (which I did not write so I
>> do not want to post it here) to verify updates on my 5.3 frankernekernel
>> I found that the kernel crashes with Oops: kernel bad access.
>>
>> I tested on latest upstream kernel build that I have at hand and the
>> result is te same (minus the message - nothing was logged and the kernel
>> simply rebooted).
> 
> That's disappointing.

It seems to work okay with qemu and mambo injection on upstream
(powernv_defconfig). I wonder why that nmi_enter is crashing.
Can you post the output of a successful test with the patch
reverted?


qemu injection test output - 
[  195.279885][    C0] Disabling lock debugging due to kernel taint
[  195.280891][    C0] MCE: CPU0: machine check (Warning) Host SLB Multihit DAR: 00000000deadbeef [Recovered]
[  195.282117][    C0] MCE: CPU0: NIP: [c00000000003c2b4] isa300_idle_stop_mayloss+0x68/0x6c
[  195.283631][    C0] MCE: CPU0: Initiator CPU
[  195.284432][    C0] MCE: CPU0: Probable Software error (some chance of hardware cause)
[  220.711577][   T90] MCE: CPU0: machine check (Warning) Host SLB Multihit DAR: 00000000deadbeef [Recovered]
[  220.712805][   T90] MCE: CPU0: PID: 90 Comm: yes NIP: [00007fff7fdac2e0]
[  220.713553][   T90] MCE: CPU0: Initiator CPU
[  220.714021][   T90] MCE: CPU0: Probable Software error (some chance of hardware cause)

Thanks,
Nick