[Skiboot] (no subject)

Nicholas Piggin npiggin at gmail.com
Fri Dec 1 02:52:13 AEDT 2017

Date: Fri, 1 Dec 2017 01:39:57 +1000
Subject: [RFC PATCH 0/2] MMU initialisation fixes

Here's a couple of MMU initialisation fixes. The first one I found
I needed in order for fast rebooting to survive. The second one
solves a similar problem with kexec (although it also solves the
fast reboot problem, it's not so nice because we would rather
completely reset the MMU registers like PTCR and LPCR for booting).

I think these should fix the immediate problem. There's a couple of
further things I want to do which are/involve Linux patches.

Firstly, Linux should set up MMU registers like PIDR properly in
its per-CPU mmu initialisation at boot, patch for that should not
be controversial.

Secondly, Linux really wants a call from firmware that puts SPRs
into a sane boot state. IMO it's no good to rely on the previous
kernel to get that exactly right. So we should have an OPAL call
for that (and an hcall on pseries platform seems like a good idea).

Either one of those would also have avoided this problem. Anyway
I think this fix (patch 2) should be workable for existing kernels.


Nicholas Piggin (2):
  head: POWER9 initialise MMU registers to boot state for fast-reboot
  core/cpu: have opal_reinit_cpus clear MMU registers

 asm/head.S          | 11 ++++++++++-
 core/cpu.c          | 43 +++++++++++++++++++++++++++----------------
 include/processor.h |  3 +++
 3 files changed, 40 insertions(+), 17 deletions(-)


More information about the Skiboot mailing list