On Thu, 2018-04-05 at 05:50:49 UTC, Nicholas Piggin wrote:
Presently the dt_cpu_ftrs restore_cpu will only add bits to the LPCR for secondaries, but some bits must be removed (e.g., UPRT for HPT). Not clearing these bits on secondaries causes checkstops when booting with disable_radix.
restore_cpu can not just set LPCR, because it is also called by the idle wakeup code which relies on opal_slw_set_reg to restore the value of LPCR, at least on P8 which does not save LPCR to stack in the idle code.
Fix this by including a mask of bits to clear from LPCR as well, which is used by restore_cpu.
This is a little messy now, but it's a minimal fix that can be backported. Longer term, the idle SPR save/restore code can be reworked to completely avoid calls to restore_cpu, then restore_cpu would be able to unconditionally set LPCR to match boot processor environment.
Fixes: 5a61ef74f269f ("powerpc/64s: Support new device tree binding for discovering CPU features") Cc: stable@vger.kernel.org # v4.12+ Signed-off-by: Nicholas Piggin npiggin@gmail.com
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/a57ac411832384eb93df4bfed2bf64
cheers