On Thu, 2018-05-10 at 12:21:48 UTC, Nicholas Piggin wrote: > Although it is often possible to recover a CPU that was interrupted > from OPAL with a system reset NMI, it's undesirable to interrupt them > for a few reasons. Firstly because dump/debug code itself needs to > call firmware, so it could hang on a lock or possibly corrupt a > per-cpu data structure if it or another CPU was interrupted from > OPAL. Secondly, the kexec crash dump code will not return from > interrupt to unwind the OPAL call. > > Call OPAL_QUIESCE with QUIESCE_HOLD before sending an NMI IPI to > another CPU, which wait for it to leave firmware (or time out) to > avoid this problem in normal conditions. Firmware bugs may still > result in a timeout and interrupting OPAL, but that is the best > option (stops the CPU, and possibly allows firmware to be debugged). > > Signed-off-by: Nicholas Piggin <npig...@gmail.com>
Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/ee03b9b4479d1302d01cebedda3518 cheers