[03/13] powerpc/64s: idle process interrupts from system reset wakeup

[Michael Ellerman]

On Tue, 2017-06-13 at 13:05:47 UTC, Nicholas Piggin wrote:
> When the CPU wakes from low power state, it begins at the system reset
> interrupt with the exception that caused the wakeup encoded in SRR1.
> 
> Today, powernv idle wakeup ignores the wakeup reason (except a special
> case for HMI), and the regular interrupt corresponding to the
> exception will fire after the idle wakeup exits.
> 
> Change this to replay the interrupt from the idle wakeup before
> interrupts are hard-enabled.
> 
> Test on POWER8 of context_switch selftests benchmark with polling idle
> disabled (e.g., always nap, giving cross-CPU IPIs) gives the following
> results:
> 
>                                 original         wakeup direct
> Different threads, same core:   315k/s           264k/s
> Different cores:                235k/s           242k/s
> 
> There is a slowdown for doorbell IPI (same core) case because system
> reset wakeup does not clear the message and the doorbell interrupt
> fires again needlessly.
> 
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/771d4304d07f080b6ce751e12f3579

cheers