[Skiboot] [PATCH 0/3] improve ability for OPAL to cope with re-entry due

[Nicholas Piggin]

The main patch of interest here is 2. This allows through a subset of
opal calls that are used in the xmon/crash path even when we have
interrupted another opal context. Idea is that stack is already trashed,
so we might as well let some messages get to the console etc.

Some of the Linux-side patches and results are posted here

https://marc.info/?l=linuxppc-embedded&m=152119458117643&w=2

Linux work is quite a bit more involved, so I would like to hopefully
get the skiboot part merged sooner, and I've just send the Linux patches
for RFC until we agree on skiboot.

I'd like to keep chipping away at skiboot robustness and debugability
vs these kinds of situations. It's slow going but I think doing it
incrementally is working okay. 

One important patch I recently posted was this one to make a quiesced
CPU safe vs reentrancy.

https://lists.ozlabs.org/pipermail/skiboot/2018-March/010729.html

Future direction would be to detect reentrant call before we touch
the stack, and then flip over to an emergency stack. Then we could
have an OPAL call to print the OPAL stack and do other debuggy stuff
which Linux crash dumps and xmon could use.

Comments?

Thanks,
Nick

Nicholas Piggin (3):
  core/opal: abort in case of re-entrant OPAL call
  core/opal: allow some re-entrant calls
  core/fast-reboot: disable fast reboot upon fundamental
    entry/exit/locking errors

 core/lock.c |  1 +
 core/opal.c | 21 ++++++++++++++++++---
 2 files changed, 19 insertions(+), 3 deletions(-)

-- 
2.16.1