On Wed, 25 Oct 2017 12:01:10 +0200
Michael Ellerman [off-list ref] wrote:

Nicholas Piggin [off-list ref] writes:

quoted

Take the DSCR value set by firmware as the dscr_default value,
rather than zero.

POWER9 recommends DSCR default to a non-zero value.

From: Nicholas Piggin <npiggin@gmail.com>
---
This has a problem that OS which set the DSCR to non-default
then kexec to Linux will be used as our default. I send a
corresponding patch to skiboot which resets SPRs in opal_reinit_cpus
which will make this do the right thing in that case.  

That doesn't work for pseries etc.

We should reset it in the kexec down path.

Okay I'll add that too. We should have a hypercall to reset all
the state for us like opal_reinit_cpus I reckon, but restoring
it before kexec isn't a bad idea even if we had such a thing.

Thanks,
Nick