Re: [PATCH v3 3/4] powerpc/64s: idle POWER9 can execute stop in virtual mode
flat view
From: Paul Mackerras <hidden>
Date: 2017-08-29 00:20:52
On Fri, Aug 25, 2017 at 02:30:35PM +1000, Nicholas Piggin wrote:
quoted hunk ↗ jump to hunk
The hardware can execute stop in any context, and KVM does not require real mode because siblings do not share MMU state. This saves a switch to real-mode when going idle. Acked-by: Gautham R. Shenoy <redacted> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> --- arch/powerpc/kernel/idle_book3s.S | 9 +++++++++ 1 file changed, 9 insertions(+)diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S index 14e97f442167..32d65ee323a0 100644 --- a/arch/powerpc/kernel/idle_book3s.S +++ b/arch/powerpc/kernel/idle_book3s.S@@ -195,7 +195,16 @@ pnv_powersave_common: std r5,_CCR(r1) std r1,PACAR1(r13) +BEGIN_FTR_SECTION + /* + * POWER9 does not require real mode to stop, and presently does not + * set hwthread_state for KVM (threads don't share MMU context), so + * we can remain in virtual mode for this. + */ + bctr +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300) /* + * POWER8
... and POWER7 too. Since that's just a comment, Reviewed-by: Paul Mackerras <redacted>