[Qemu-ppc] pseries on qemu-system-ppc64le crashes in doorbell_core_ipi()

[Sebastian Andrzej Siewior]

On 2019-03-29 16:20:51 [+1100], Suraj Jitindar Singh wrote:
> 
> Yeah the kernel must have used msgsndp which isn't implemented for TCG
> yet. We use doorbells in linux but only for threads which are on the
> same core.

It is msgsndp as per instruction decode.

> And when I try to construct a situation with more than 1 thread per
> core (e.g. -smp 4,threads=4), I get "TCG cannot support more than 1
> thread/core on a pseries machine".
>
> So I wonder why the guest thinks it can use msgsndp...

I see
|# cat /sys/devices/system/cpu/cpu*/topology/thread_siblings_list
|0
|1
|2
|3

so this works all well. The problem is when a CPU sends an IPI to itself
then linux's doorbell_try_core_ipi() considers this as a valid sibling
and here we have the msgsndp.

Sebastian