Subject: Re: powerpc/64s: Fix dt_cpu_ftrs to have restore_cpu clear unwanted LPCR bits

From: Michael Ellerman <[email-masked]>
Date: Fri, 6 Apr 2018 00:42:52 +1000 (AEST)

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: [email-masked] # v4.12+
> Signed-off-by: Nicholas Piggin <[email-masked]>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/a57ac411832384eb93df4bfed2bf64

cheers