core/fast-reboot: improve NMI handling during fast reset
core/fast-reboot: improve NMI handling during fast reset

Improve sreset and MCE handling in fast reboot. Switch the HILE bit
off before copying OPAL's exception vectors, so NMIs can be handled
properly. Also disable MSR[ME] while the vectors are being overwritten.

Some of the remaining problem cases are documented in comments.

Signed-off-by: Nicholas Piggin <24829078df5003d9dd1dd871ca2aeb0b1cf95ef4@gmail.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.ibm.com>

open-power/skiboot,legoater/skiboot,legoater/skiboot,legoater/skiboot,open-power/skiboot,stewart-ibm/skiboot,legoater/skiboot,open-power/skiboot,shenki/skiboot,shenki/skiboot,qemu/skiboot,stewart-ibm/skiboot,open-power/skiboot,stewart-ibm/skiboot,shenki/skiboot,qemu/skiboot,qemu/skiboot,shenki/skiboot,open-power/skiboot,shenki/skiboot,qemu/skiboot,legoater/skiboot,qemu/skiboot