Comment # 7 on bug 1083836 from Takashi Iwai

(In reply to Jiri Slaby from comment #4)
> This is no problem as sp0 and sp1 are identical (mostly, I guess) until:
>  patches.suse/x86-entry-64-use-a-per-cpu-trampoline-stack.patch
> which starts using sp0 for per_cpu stack. It obviously breaks
> current_thread_info() inlined in KMPs.

So, can we fix this somehow?  It shouldn't be impossible to detect the old KMP
code path and switch the mechanics, but I'm not sure whether it's practically
feasible at all...

Alternatively, we may disallow to run the old code from the old KMP, not only
warning of spectre v2 vulnerability.  We'll end up upgrading all our own KMPs
in anyway together with the kernel update.
But still it'll be a problem if the system requires the 3rd party KMP
inevitably (e.g. for storage); then the system will be non-bootable.

Any ideas?